Friday, September 4, 2009
Thursday, March 12, 2009
Interveiw Question
Quick Notes - LAN
What is carrier sense multiple access collision detect (CSMA/CD)?
CSMA/CD describes the Ethernet access method. In CSMA/CD, many stations can transmit on the same cable, and no station has priority over any other. Before a station transmits, it listens on the wire to make sure no other station is transmitting. If no other station is transmitting, the station transmits across the wire. CSMA/CD is all about devices taking turns using the wire.
What are MAC addresses?
For computers to identify each other on the data link layer, they need a MAC address (hardware address). All devices on a LAN must have a unique MAC address. A MAC address is a 48-bit (six octet) address burned into a network interface card. The first three octets (24 bits) of the MAC address indicate the vendor that manufactured the card. This is called the Organization Unique Identifier (OUI). The last three octets of the MAC address are the unique host address. An example of a MAC address is 00-80-C6-E7-9C-EF.
What are the three types of LAN traffic?
The three types of LAN traffic are:
Unicasts
Broadcasts
Multicasts
What are unicast frames?
Unicast frames are the most common type of LAN traffic. A unicast frame is a frame intended for only one host. In unicast frames, the only station that processes the frame is the station that has its own MAC address in the destination portion of the packet.
What are broadcast frames?
Broadcast frames are frames intended for everyone. Stations view broadcast frames as public service announcements. All stations receive and process broadcast frames. In large networks, broadcasts can bring the network to a crawl, because every computer must process them.
What is the destination address of broadcast frames?
The destination address of broadcast frames (Layer 2 broadcast addresses) is FF-FF-FF-FF-FF-FF, or all 1s in binary.
What are multicast frames?
Multicast frames address a group of devices that have a common interest. These frames allow the source to send only one copy of the frame on the network even though it is intended for several stations. Only stations that have a card that is configured to receive multicast frames process them. All other stations discard multicast frames.
What devices can you use to segment a LAN at Layer 1, Layer 2, and Layer 3?
Three devices you can use to segment a LAN are:
Hubs/repeaters (Layer 1)
Bridges/switches (Layer 2) - physical addresses
Routers (Layer 3) - logical addresses
What happens when you segment the network with hubs/repeaters?
Because hubs and repeaters operate at the physical layer of the OSI model, segmenting a network with these devices appears as an extension to the physical cable. Hubs and repeaters are transparent to devices. They are unintelligent devices. All devices that connect to a hub/repeater share the same bandwidth. Hubs/repeaters create a single broadcast and collision domain.
What is the advantage of segmenting a network with bridges/switches?
Bridges/switches operate at Layer 2 of the OSI model and filter by MAC address. Each port on a bridge/switch provides full-dedicated bandwidth and creates a single collision domain. Because bridges/switches operate at Layer 2 of the OSI model, they cannot filter broadcasts, and they create a single broadcast domain. For the CCNA test, remember that switches create more collision domains and fewer collisions.
What is the difference between bridges and switches?
Bridges and switches function the same way; the only difference is in how they are implemented. Bridges are implemented by software and usually have a couple of network ports. Switches are implemented in hardware by ASIC chips and have many ports.
What are the advantages and disadvantages of segmenting the LAN with routers?
An advantage of segmenting the LAN with routers is that each interface on a router creates a single broadcast and collision domain. Routers operate at Layer 3 of the OSI model and do not propagate broadcasts. Some disadvantages are that routers are not transparent and are implemented in software, thus introducing latency in the network.
What is the Maximum Transmission Unit (MTU) for an Ethernet frame?
1500 bytes is the MTU for an Ethernet frame. You will notice that some publications state that the MTU for Ethernet is 1518 bytes. This is correct also. But what is the true answer? The MTU for Ethernet, including the header, source and destination address, data, and CRC is 1518 bytes. The MTU for the data portion of the frame is 1500 bytes.
What three major functions do Layer 2 switches provide?
The three major functions that Layer 2 switches provide are
Address learning
Packet forwarding/filtering
Loop avoidance by spanning tree
What are some advantages of switches?
Some advantages of switches are as follows:
They increase available network bandwidth.
They reduce the number of users per segment.
They provide dedicated bandwidth to each segment.
Transparent bridging (switching) provides five bridging functions to determine what to do when it receives a frame.
What are these five processes?
The five processes are:
Learning
Flooding
Filtering
Forwarding
Aging
In transparent bridging, what is the learning process?
The first process a bridge goes through when it is powered on is the learning process. The MAC address table on the bridge contains no entries, and the bridge goes through the learning process to record all workstations on every interface. In the learning process, the bridge records the source MAC address and source port number in the MAC address table every time it sees a frame.
In transparent bridging, what is the flooding process?
When a bridge is first turned on, it has no MAC address in its table. When a switch receives a unicast frame, it knows the source address and port from which the unicast frame came, but no entry exists in its table for the destination address. This is called an unknown unicast frame. When a switch receives an unknown unicast frame, it sends the frame out all forwarding interfaces on the bridge except the interface that received the frame. This process is the flooding process.
In transparent bridging, what is the filtering process?
The filtering process occurs when the source and destination addresses reside on the same interface on the bridge. Because the bridge does not need to forward a frame in which the destination and source addresses reside on the same interface, it filters the frame and discards it.
In transparent bridging, what is the forwarding process?
The forwarding process occurs when a switch receives a unicast frame and has an entry of the destination address in its MAC table. The switch then forwards the frame to the interface where that destination address resides.
In transparent bridging, what occurs during the aging process?
Every time a bridge learns a source address, it time-stamps the entry. When the bridge sees a frame from this source, it updates the time stamp. If the bridge does not hear from the source for a specific amount of time (called the aging timer), the bridge deletes the entry from its MAC address table. This process is the aging process.
What is the default aging time in transparent bridges?
The default aging timer is 5 minutes.
What is the Spanning-Tree Protocol (STP)?
STP is a loop-prevention bridge-to-bridge protocol. Its main purpose is to dynamically maintain a loop-free network. It does this by sending out Bridge Protocol Data Units (BPDUs), discovering any loops in the topology, and blocking one or more redundant links.
How does STP maintain a loop-free network?
STP maintains a loop-free network by
Electing a root bridge
Electing a root port on each nonroot bridge
Electing designated ports
Putting in the blocking state any port that is not a root port or designated port
In spanning tree, what is a Bridge ID (BID)?
A BID is an 8-byte field that is composed of the bridge's 6-byte MAC address and a 2-byte bridge priority.
What is the default bridge priority in a Bridge ID for all Cisco switches?
32,768
In spanning tree, what is path cost?
Path cost is a calculation to determine the link's bandwidth. It is a value assigned to each port that is based on the port's speed.
What is the spanning tree path cost for each of the following?
10 Mbps
100 Mbps
1 Gbps
The path costs are as follows:
10 Mbps - 100
100 Mbps - 19
1 Gbps - 4
When calculating a loop-free environment, what four-step decision sequence does spanning tree use to determine what will be the root bridge and which ports will forward or block?
The four-step decision sequence that spanning tree uses to determine the root bridge and which port will forward is as follows:
Step 1. The lowest root BID
Step 2. The lowest path cost to the root bridge
Step 3. The lowest sender BID
Step 4. The lowest port ID
How do bridges pass spanning tree information between themselves?
Bridges pass STP information using special frame called Bridge Protocol Data Units (BPDUs).
How often do bridges send BPDUs out active ports?
The default time that bridges send BPDUs out active ports is 2 seconds.
Note: All ports on a switch listen for BPDUs in case there is a topology change.
In STP, how is a root bridge elected?
In STP, the bridge with the lowest BID is elected the root bridge. All ports on the root bridge are placed in the forwarding state and are called designated ports.
Note: The BID is a 6-byte field that is composed of a default priority (32,768) and a MAC address. Because all Cisco switches use the default priority, the switch with the lowest MAC address is elected the root bridge. As a rule of thumb, lower will always win in spanning tree.
After bridges elect the root bridge, what do they do next?
After electing the root bridge, switches elect root ports. A root port is the port on nonroot bridges that is closest to the root bridge. Every nonroot bridge must select one root port.
How do nonroot bridges decide which port they will elect as a root port?
Nonroot bridges use root path cost to determine which port will be the root port. Root path cost is the cumulative cost of all links to the root bridge. The port with the lowest root path cost is elected the bridge's root port and is placed in the forwarding state.
What is the difference between path cost and root path cost?
Path cost is the value assigned to each port. It is added to BPDUs received on that port to calculate the root path cost. Root path cost is defined as the cumulative cost to the root bridge. In a BPDU, this is the value transmitted in the cost field. In a bridge, this value is calculated by adding the receiving port's path cost to the value contained in the BPDU.
If a nonroot bridge has two redundant ports with the same root path cost, how does the bridge choose which port will be the root port?
If a nonroot bridge has redundant ports with the same root path cost, the deciding factor is the port with the lowest port ID (port number).
After the root bridge and root ports are selected, the last step in spanning tree is to elect designated ports. How do bridges elect designated ports?
In spanning tree, each segment in a bridged network has one designated port. This port is a single port that both sends and receives traffic to and from that segment and the root bridge. All other ports are placed in a blocking state. This ensures that only one port on any segment can send and receive traffic to and from the root bridge, ensuring a loop-free topology. The bridge containing the designated port for a segment is called the designated bridge for that segment. Designated ports are chosen based on cumulative root path cost to the root bridge.
Note: Every active port on the root bridge becomes a designated port.
If a bridge is faced with a tie in electing designated ports, how does it decide which port will be the designated port?
In the event of a tie, STP uses the four-step decision process discussed in Question 30. It first looks for the BPDU with the lowest BID; this is always the root bridge. If the switch is not the root bridge, it moves to the next step: the BPDU with the lowest path cost to the root bridge. If both paths are equal, STP looks for the BPDU with the lowest sender BID. If these are equal, STP uses the link with the lowest port ID as the final tiebreaker.
What are the four spanning tree port states?
The four spanning tree port states are
Blocking
Listening
Learning
Forwarding
Remember that root and designated ports forward traffic and that nondesignated ports block traffic but still listen for BPDUs.
Important note: There is another port state - Disabled - (No frames forwarded, no BPDUs heard). If it shows up in the answer options - select it along with the others.
What is the STP blocking state?
When a switch starts, all ports are in the blocking state. This is to prevent any loops in the network. If there is a better path to the root bridge, the port remains in the blocked state. Ports in the blocked state cannot send or receive traffic, but they can receive BPDUs.
What is the STP listening state?
Ports transition from a blocked state to a listening state. In this state, no user data is passed. The port only listens for BPDUs. After listening for 15 seconds (if the bridge does not find a better path), the port moves to the next state, the learning state.
What is the STP learning state?
In the STP learning state, no user data is being passed. The port quietly builds its bridging table. The default time in the learning state is 15 seconds.
What is the STP forwarding state?
After the default time in the learning state is up, the port moves to the forwarding state. In the forwarding state, the port sends and receives data.
What is STP forward delay?
The forward delay is the time it takes for a port to move from the listening state to the learning state or from the learning state to the forwarding state. The default time is 30 seconds.
What is the hello time in STP timers?
The hello time is the time interval between the sending of BPDUs. The default time is 2 seconds.
What is the Max Age timer?
The Max Age timer is how long a bridge stores a BPDU before discarding it. The default time is 20 seconds (ten missed hello intervals).
What is the default time a port takes to transition from the blocking state to the forwarding state?
The default time a port takes to transition from the blocking state to the forwarding state is 50 seconds: 20 seconds for Max Age, 15 seconds for listening, and 15 seconds for learning.
What does STP do when it detects a topology change in the network due to a bridge or link failure?
If spanning tree detects a change in the network due to a bridge or link failure, at least one bridge interface changes from the blocking state to the forwarding state, or vice versa.
WAN
The three WAN connection types available are leased lines, circuit-switched, and packet-switched. Define the differences between each connection type.
Leased lines are dedicated point-to-point lines that provide a single preestablished WAN communication path from the customer's network to the remote network. Leased lines are usually employed over synchronous connections. They are generally expensive and are always up.
Circuit-switched connections are dedicated for only the duration of the call. The telephone system and ISDN are examples of circuit-switched networks. Packet-switched connections use virtual circuits (VCs) to provide end-to-end connectivity.
Packet-switched connections are similar to leased lines, except that the line is shared by other customers. A packet knows how to reach its destination by programming of switches. Frame Relay is an example of a packet-switched connection.
Define customer premises equipment (CPE), and give an example.
CPE is equipment that is located on the customer's (or subscriber's) premises. It is equipment owned by the customer or equipment leased by the service provider to the customer. An example is your router.
What is the demarcation point (demarc)?
The demarc is the point where the CPE ends and the local loop begins. It is the last responsibility of the service provider and is usually an RJ-45 jack located close to the CPE. Think of the demarc as the boundary between the customer's wiring and the service provider's wiring.
What is the local loop?
The local loop is the physical cable that extends from the demarc to the central office.
Describe the central office (CO).
The CO is the telco switching facility that connects the customer to the provider's switching network. The CO is sometimes referred to as a point of presence. It is the point where the local loop gains access to the service provider's access lines.
What is the toll network?
All the telco switches, COs, and trunk lines inside the WAN provider's network are the toll network.
What are synchronous links?
Synchronous links have identical frequencies and contain individual characters encapsulated in control bits, called start/stop bits, that designate the beginning and end of each character. Synchronous links try to use the same speed as the other end of a serial link.
What are Asynchronous links?
Asynchronous links send digital signals without timing. Asynchronous links agree on the same speed, but there is no check or adjustment of the rates if they are slightly different. Only 1 byte per transfer is sent.
List some typical Layer 2 encapsulation methods for WAN links.
. High-Level Data Link Control (HDLC)
• Point-to-Point Protocol (PPP)
• Serial Line Internet Protocol (SLIP)
• X.25/Link Access Procedure, Balanced (LAPB)
• Frame Relay• Asynchronous Transfer Mode (ATM)
Describe HDLC.
HDLC was derived from Synchronous Data Link Control (SDLC). It is the default encapsulation type on point-to-point dedicated links and circuit-switched connections between Cisco routers. It is an ISO-standard bit-oriented data-link protocol that encapsulates data on synchronous links. HDLC is a connection-oriented protocol that has very little overhead. HDLC lacks a protocol field and therefore cannot encapsulate multiple network layer protocols across the same link. Because of this, each vendor has its own method of identifying the network-layer protocol. Cisco offers a propriety version of HDLC that uses a type field that acts as a protocol field, making it possible for multiple network-layer protocols to share the same link.
By default, Cisco uses HDLC as its default encapsulation method across synchronous lines (point-to-point links). If a serial line uses a different encapsulation protocol, how do you change it back to HDLC?
To change a serial line back to HDLC, use the following interface command on the serial interface you want to change: Router(config-if)#encapsulation hdlc
What is the Point-to-Point Protocol (PPP)?
PPP is an industry-standard protocol that provides router-to-router or router-to-host connections over synchronous and asynchronous links. It can be used to connect to other vendors' equipment. It works with several network-layer protocols, such as IP and IPX. PPP provides authentication through PAP or CHAP.
Describe X.25/LAPB.
X.25/LAPB is an ITU-T standard that has a tremendous amount of overhead because of its strict timeout and windowing techniques. LAPB is the connection-oriented protocol used with X.25. It uses the ABM (Asynchronous Balance Mode) transfer mode. X.25/LAPB was used in the 1980s when WAN links were not as error-free as they are today. X.25 is a predecessor of Frame Relay. X.25 supports both switched and permanent virtual circuits.
What is Frame Relay?
An industry standard, Frame Relay is a switched data link layer protocol that uses virtual circuits to identify the traffic that belongs to certain routers. It provides dynamic bandwidth allocation and congestion control.
Quick Notes - INTERNETWORKING
What are the three layers of the Cisco Hierarchical Model?
The three layers of the Cisco Hierarchical Model are: 1
the access layer
The distribution layer
The core layer
In the Cisco Hierarchical Model, what is the function of the access layer?
Sometimes referred to as the desktop layer, the access layer is the point at which users connect to the network through low-end switches. Some functions of the access layer include:
Connectivity into the distribution layer
Shared Bandwidth
MAC Address filtering (switching)
Segmentation
What is the function of the distribution layer in the Cisco Hierarchical Model?
The distribution layer is also known as the workgroup layer. It is the demarcation point between the access and core layers of the network. Its primary function is to provide routing, filtering, and WAN access. The distribution layer determines how packets access the core, so it is the layer at which to implement policy-based connectivity. Some functions include the following:
Collection point for access layer devices
Broadcast and multicast domain segmentation
Security and filtering services such as firewalls and access lists
Providing translation between different media types
Inter-VLAN routing
What is the role of the core layer in the Cisco Hierarchical Model?
The core layer is the backbone of the network. Its main function is to switch traffic as fast as possible. Therefore, it should not perform any filtering to slow down traffic.
The ISO's OSI Reference Model contains seven layers. What are they? Include the layer number and name of each layer in your answer.
The seven layers of the OSI model are as follows:
Layer 7 - Application layer
Layer 6 - Presentation layer
Layer 5 - Session layer
Layer 4 - Transport layer
Layer 3 - Network layer
Layer 2 - Data link layer
Layer 1 - Physical layer
What are some reasons that the industry uses a layered model?
Here are some reasons why the industry uses a layered model:
It encourages industry standardization by defining what functions occur at each level.
It allows vendors to modify or improve components at only one layer versus rewriting the whole protocol stack.
It helps interoperability by defining standards for the operations at each level.
It helps with troubleshooting.
What does the application layer (Layer 7) of the OSI model do, and what are some examples of this layer?
The application layer is the layer that is closest to the user. This means that this layer interacts directly with the software application. The application layer's main function is to identify and establish communication partners, determine resource availability, and synchronize communication. Some examples include the following:
TCP/IP applications such as Telnet, File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), WWW, and HTTP.
OSI applications such as Virtual Terminal Protocol, File
Transfer, Access, and Management (FTAM), and Common Management Information Protocol (CMIP).
In the OSI model, what are the responsibilities of the presentation layer (Layer 6)? Give some examples of this layer.
Also known as the translator, the presentation layer provides coding and conversion functions to application layer data. This guarantees that the application layer on another system can read data transferred from the application layer of a different system. Some examples of the presentation layer are:
Compression, decompression, and encryption
JPEG, TIFF, GIFF, PICT, QuickTime, MPEG, and ASCII
What are the functions of the session layer (Layer 5)? Give some examples.
The session layer is responsible for creating, managing, and ending communication sessions between presentation layer entities. These sessions consist of service requests and responses that develop between applications located on different network devices. Some examples include SQL, RPC, NFS, X Window System, ZIP, NetBIOS names, and AppleTalk ASP.
What is the transport layer (Layer 4) responsible for? Give some examples of transport layer implementations.
The transport layer segments and reassembles data from upper-layer applications into data streams. It provides reliable data transmission to upper layers. End-to-end communications, flow control, multiplexing, error detection and correction, and virtual circuit management are typical transport layer functions. Some examples include TCP, UDP*, and SPX.
Note: watch out for end-to-end on communications on the exam! Transport layer.
* Error correction does not apply to UDP - connection-less - unreliable.....
What is flow control, and what are the three methods of implementing it?
Flow control is the method of controlling the rate at which a computer sends data, thus preventing network congestion. The three methods of implementing flow control are
Buffering
Congestion avoidance
Windowing
Almost certain to be on the exam.
Describe the function of the network layer (Layer 3), and give some examples of network layer implementations.
The network layer provides internetwork routing and logical network addresses. It defines how to transport traffic between devices that are not locally attached. The network layer also supports connection-oriented and connectionless service from higher-layer protocols. Routers operate at the network layer. IP, IPX, AppleTalk, and DDP are examples of network layer implementations.
Are network layer addresses physical or logical?
Network layer addresses are logical addresses specific to the network layer protocol being run on the network. Each network layer protocol has a different addressing scheme. They are usually hierarchical and define networks first and then host or devices on that network. An example of a network address is an IP address, which is a 32-bit address often expressed in decimal format. 192.168.0.1 is an example of an IP address in decimal format.
How do routers function at the network layer of the OSI model?
Routers learn, record, and maintain awareness of different networks. They decide the best path to these networks and maintain this information in a routing table. The routing table includes the following:
Network addresses, which are protocol-specific. If you are running more than one protocol, you have a network address for each protocol.
The interface the router uses to route a packet to a different network.
A metric, which is the distance to a remote network or the weight of the bandwidth, load, delay, and reliability of the path to the remote network.
Routers create broadcast domains. One interface on a router creates a single broadcast domain and collision domain. However, an interface on a switch creates only a single collision domain.
In addition to learning the remote network and providing a path to the network, what other functions do routers carry out?
Routers perform these tasks:
Routers, by default, do not forward broadcasts or multicasts.
Routers can perform bridging and routing functions.
If a router has multiple paths to a destination, it can determine the best path to the destination.
Routers forward traffic based on Layer 3 destination addresses.
Routers can connect Virtual LANs (VLANs).
Routers can provide quality of service for specified types of network traffic.
What is the responsibility of the data link layer (Layer 2)?
The data link layer provides functional and procedural means for connectionless mode among network entities, and for connection mode entities it provides the establishment, maintenance, and release of data link connections among network entities and for the transfer of data link service data units. The data link layer translates messages from the network layer into bits for the physical layer, and it enables the network layer to control the interconnection of data circuits within the physical layer. Its specifications define different network and protocol characteristics, including physical addressing, error notification, network topology, and sequencing of frames. Data link protocols provide the delivery across individual links and are concerned with the different media types, such as 802.2 and 802.3. The data link layer is responsible for putting 1s and 0s into a logical group. These 1s and 0s are then put on the physical wire. Some examples of data link layer implementations are IEEE 802.2/802.3, IEEE 802.5/802.2, packet trailer (for Ethernet, the FCS or CRC), FFDI, HDLC, and Frame Relay.
The IEEE defines what two sublayers of the data link layer?
The two sublayers of the data link layer are
The Logical Link Control (LLC) sublayer
The Media Access Control (MAC) sublayer
These two sublayers provide physical media independence.
For what is the LLC sublayer responsible?
The Logical Link Control (802.2) sublayer is responsible for identifying different network layer protocols and then encapsulating them to be transferred across the network. An LLC header tells the data link layer what to do with a packet after it is received.
What functions does the Media Access Control (MAC) sublayer provide?
The MAC sublayer specifies how data is placed and transported over the physical wire. The LLC layer communicates with the network layer, but the MAC layer communicates downward directly to the physical layer. Physical addressing (MAC addresses), network topologies, error notification, and delivery of frames are defined at this sublayer.
What are some network devices that operate at the data link layer?
Bridges and switches are network devices that operate at the data link layer. Both devices filter traffic by MAC addresses.
What is the function of the OSI model's physical layer (Layer 1)? Give some examples of physical layer implementations.
The physical layer defines the physical medium. It defines the media type, the connector type, and the signaling type (baseband versus broadband). This includes voltage levels, physical data rates, and maximum cable lengths. The physical layer is responsible for converting frames into electronic bits of data, which are then sent or received across the physical medium. Twisted pair, coaxial cable, and fiber-optic cable operate at this level. Other implementations at this layer are repeaters/hubs, RJ-45.
The Ethernet and IEEE 802.3 standards define what three physical wiring standards that operate at 10 Mbps?
These physical wiring standards operate at 10 Mbps:
10Base2
10Base5
10BaseT
What are collision domains?
In Ethernet segments, devices connect to the same physical medium. Because of this, all devices receive all signals sent across the wire. If two devices send a packet at the same time, a collision occurs. In the event of a collision, the two devices run a backoff algorithm and resend the packet. The devices retransmit up to 15 times. The first station to detect a collision issues a jam signal. When a jam signal is sent from a workstation, it affects all of the machines on the segment, not just the two that collided; when the jam signal is on the wire, no workstations can transmit data. The more collisions that occur in a network, the slower it will be, because the devices will have to resend the packet. A collision domain defines a group of devices connected to the same physical medium.
What are broadcast domains?
A broadcast domain defines a group of devices that receive each others' broadcast messages. As with collisions, the more broadcasts that occur on the network, the slower your network will be. This is because every device that receives a broadcast must process it to see if the broadcast is intended for it.
What devices are used to break up collision and broadcast domains?
Switches and bridges are used to break up collision domains. They create more collision domains and fewer collisions. Routers are used to break up broadcast domains. They create more broadcast domains and smaller broadcast areas.
How do the different layers of the OSI model communicate with each other?
Each layer of the OSI model can communicate only with the layer above it, below it, and parallel to it (a peer layer). For example, the presentation layer can communicate with only the application layer, session layer, and presentation layer on the machine it is communicating with. These layers communicate with each other using protocol data units (PDUs). These PDUs control information that is added to the user data at each layer of the model. This information resides in fields called headers (the front of the data field) and trailers (the end of the data field).
What is data encapsulation?
A PDU can include different information as it goes up or down the OSI model. It is given a different name according to the information it is carrying (the layer it is at). When the transport layer receives upper layer data, it adds a TCP header to the data; this is called a segment. The segment is then passed to the network layer, and an IP header is added; thus, the data becomes a packet. The packet is passed to the data link layer, thus becoming a frame. This frame is then converted into bits and is passed across the network medium. This is data encapsulationApplication layer -- Data
Transport layer -- Segment
Network layer -- Packet
Data link layer -- Frame
There is also the Physical Layer -- Bits
What is the difference between a routing protocol and a routed protocol?
Routing protocols determine how to route traffic to the best location of a routed protocol. Examples of routing protocols are RIP, EIGRP, OSFP, and BGP. Examples of routed protocols are IP and IPX.
What 3 devices are used to segment a LAN?
Router
Switch
Bridge
Quick Notes - CABLING TECHNOLOGY
What is a straight-through cable, and when would you use it?
A straight-through cable is the same at both ends. A straight-through cable uses pins 1, 2, 3, and 6. The send and receive wires are not crossed. You should use a straight-through cable when connecting dissimilar devices. Examples include connecting PCs to switches or hubs or a router to a switch or a hub.
What is a crossover cable, and when would you use it?
A crossover cable is a cable that has the send and receive wires crossed at one of the ends. On a Category 5 cable, the 1 and 3 wires and the 2 and 6 wires are switched on one of the cable's ends. You should use a crossover cable when connecting similar devices, such as connecting a router to a router, a switch to a switch or hub, a hub to a hub, or a PC to a PC.
Important tip -- Router (think of it as a PC) to PC via 10BaseT (NIC) uses a "crossover cable". (contradicts the rule)
How do you set up a console session to a Cisco device?
To set up a console session to a Cisco device, you connect a rollover cable to the console port on the Cisco device. You then connect the other end to your PC and configure a terminal emulation application to the following com settings: 9600 bps, 8 data bits, no parity, 1 stop bit, and no flow control.
What is the maximum cable length for each of the following?
The maximum cable lengths are as follows:
10Base2 (thinnet) 185 meters
10Base5 (thicknet) 500 meters
10BaseT 100 meters
10BaseFL 2000 meters (400 meters in a shared environment and 2000 meters in a point-to-point environment)
100BaseT 100 meters
What does Base stand for in 10BaseT and 100BaseT?
Base in 10BaseT and 100BaseT stands for baseband. Baseband is a network technology in which only one carrier frequency (signal) is used.
What is the difference between baseband and broadband?
Baseband is a network technology in which only one carrier frequency is used (such as Ethernet). Broadband is a network technology in which several independent channels are multiplexed into one cable (for example, a T1 line).
Quick Notes - ACCESS LISTS
Besides named access lists, what are the two types of IP access lists?
The two types of IP access lists are standard and extended.
What criteria do standard IP access lists use to filter packets?
Standard IP access lists filter packets by the source address. This results in the packet's being permitted or denied for the entire protocol suite based on the source network IP address.
What criteria do extended IP access lists use to filter packets?
Extended IP access lists filter packets by source address, destination address, protocols, and port numbers.
In what two ways can IP access lists be applied to an interface?
Access lists can be applied as inbound or outbound access lists. Inbound access lists process packets as they enter a router's interface and before they are routed. Outbound access lists process packets as they exit a router's interface and after they are routed.
How many access lists can be applied to an interface on a Cisco router?
Only one access list per protocol, per direction, per interface can be applied on a Cisco router. Multiple access lists are permitted per interface, but they must be for a different protocol.
How are access lists processed?
Access lists are processed in sequential, logical order, evaluating packets from the top down, one statement at a time. As soon as a match is made, the permit or deny option is applied, and the packet is not applied to any more access list statements. Because of this, the order of the statements within any access list is significant.
What is at the end of each access list?
At the end of each access list, an implicit deny statement denies any packet not filtered in the access list.
What are the number ranges used to define standard and extended IP access lists?
The number ranges used to define standard and extended IP access lists are as follows:
• Standard IP access lists 1 to 99 and 1300 to 1999• Extended IP access lists 100 to 199 and 2000 to 2699
When implementing access lists, what are wildcard masks?
Wildcard masks define the subset of the 32 bits in the IP address that must be matched. Wildcards are used with access lists to specify a host, network, or part of a network. Wildcard masks work exactly the opposite of subnet masks. In subnet masks, 1 bits are matched to the network portion of the address, and 0s are wildcards that specify the host range. In wildcard masks, when 0s are present, the octet address must match.
What is the IOS command syntax used to create a standard IP access list?
Here is the command syntax to create a standard IP access list:
access-list access-list-number {permit deny} source-address [wildcard mask]access-list-number is a number from 1 to 99.
For example:
RouterA(config)#access-list 10 deny 192.168.0.0 0.0.0.255
How can you display all access lists on a Cisco router?
To display all access lists on a Cisco router, use the show access-list command: RouterA#show access-list Standard IP access list 10 deny 192.168.0.0, wildcard bits 0.0.0.255Extended IP access list 101 permit tcp any any eq www permit udp any any eq domain permit udp any eq domain any permit icmp any any deny tcp 192.168.10.0 0.0.0.255 any eq wwwRouterA#
Quick Notes - FRAME RELAY
What protocol does Frame Relay rely on for error checking?
Frame Relay does not rely on any certain protocol for error checking. Instead, it relies on upper-layer protocols to provide error checking. For example, Frame Relay relies on TCP to provide error checking in an IP network.
At what layers of the OSI model does Frame Relay operate?
Frame Relay operates at the two lower layers of the OSI model (data link and physical).
What is the difference between switched virtual circuits (SVCs) and permanent virtual circuits (PVCs)?
SVCs are virtual circuits that are dynamically established when data needs to be transferred and that are terminated when data transmission is complete. SVCs consist of four states: call setup, data transfer, idle, and call termination. PVCs are permanently established virtual circuits that operate in one of two states: idle or data transfer. When the PVC is idle, the connection between the DTE devices is still active.
What is a Data Link Connection Identifier (DLCI)?
A DLCI is a number that identifies the logical circuit between the router and the Frame Relay switch. It is the Frame Relay Layer 2 address. The Frame Relay switch maps DLCIs between each pair of routers to create a PVC. For IP devices at the end of each virtual circuit to communicate, their IP addresses need to be mapped to DLCIs. If you are running Cisco IOS 11.2 or later, mapping is done automatically using Inverse ARP. DLCIs have local significance. Think of DLCIs as the MAC address of the Frame Relay network.
What is the committed information rate (CIR)?
The CIR is the committed information rate, by the service provider, in bits per second, at which data will be transferred. The service provider sends any data in excess of this rate if its network has capacity at that time.
How does Frame Relay use Inverse ARP?
Frame Relay uses Inverse ARP as a way to dynamically map a network layer address to a DLCI. With Inverse ARP, the router can discover the network address of a device associated with a VC.
What is the Local Management Interface (LMI)?
The LMI is a signaling standard between a CPE device (a router) and the Frame Relay switch that is responsible for managing and maintaining status between the devices. It is autosensed with Cisco IOS Release 11.2 and later.
In Frame Relay, what is Forward Explicit Congestion Notification (FECN)?
The FECN is the bit in the Frame Relay header that signals to anyone receiving the frame (switches and DTEs) that congestion is occurring in the same direction as the frame. Switches and DTEs can react by slowing the rate at which data is sent in that direction.
What is Backward Explicit Congestion Notification (BECN)?
The BECN is the bit in the Frame Relay header that signals to switches and DTEs receiving the frame that congestion is occurring in the direction opposite (backward) that of the frame. If switches and DTE devices detect that the BECN bit in the Frame Relay header is set to 1, they slow the rate at which data is sent in that direction.
In the Frame Relay header, what is the discard eligibility (DE) bit?
If congestion is detected on the Frame Relay network, the DE bit is turned on in the Frame Relay header. The DE bit is turned on for frames that are in excess of the CIR. The DE bit tells a switch which frames to discard if they must be discarded.
What is the default LMI type for Cisco routers that are configured for Frame Relay?
The default LMI for Cisco routers configured for Frame Relay is Cisco. If you are running Cisco IOS Release 11.2 or later, the Cisco router tries to autosense which LMI type the Frame Relay switch is using. If it cannot autosense the LMI type, the router uses Cisco as its LMI type. The three types of LMIs supported by Cisco routers are:
Cisco
ANSI
Q933a
When a router receives LMI information, it updates its VC status to one of three states. What are these three states?
The three states that a VC uses to update its status are as follows:
Active state The connection is active, and routers can exchange data.
Inactive state The local connection to the Frame Relay switch is working, but the remote router's connection to the Frame Relay switch is not working.
Deleted state Indicates that no LMIs are being received from the Frame Relay switch or that there is no service between the router and the Frame Relay switch.
How do you enable Frame Relay on a Cisco router?
To enable Frame Relay on a Cisco router, you must first enable the serial interface for Frame Relay encapsulation with the encapsulation frame-relay interface command:
RouterB(config)#int s 0
RouterB(config-if)#ip address 192.168.1.1 255.255.255.0
RouterB(config-if)#encapsulation frame-relay
The default encapsulation for a serial interface configured for Frame Relay is cisco. If you are connecting to a non-Cisco router, how do you change the encapsulation type?
If you are connecting to a non-Cisco router in a Frame Relay network, you need to specify ietf as the encapsulation type:
RouterB(config-if)#ip address 192.168.1.1 255.255.255.0
RouterB(config-if)#encapsulation frame-relay ietf
If you are using Cisco IOS Release 11.1 or earlier, or if you do not want to autosense the LMI type, how do you define the LMI type on a Cisco router?
To define the LMI type on a Cisco router, use the frame-relay lmi-type {ansi cisco q933a} interface command:
RouterB(config-if)#ip address 192.168.1.1 255.255.255.0
RouterB(config-if)#encapsulation frame-relay
RouterB(config-if)#frame-relay lmi-type ansi
If Inverse ARP is disabled on your router, how do you reenable it?
Inverse ARP is enabled by default on a Cisco router. If it is disabled, reenable it by using the following command:
RouterB(config-if)#frame-relay inverse-arp [protocol] [dlci]
Supported protocols indicated by the protocol option include ip, ipx, decnet, appletalk, vines, and xns.
If a remote router does not support Inverse ARP, you must define the address-to-DLCI table
statically. How do you create these static maps?
To define static maps on a Cisco router, use the following command:
RouterA(config-if)#frame-relay map protocol protocol-address dlci [broadcast] [ietf cisco] [payload-compress packet-by-packet]
where:
• protocol defines the supported protocol bridging or LLC.
• protocol-address is the remote router's network layer address.
• dlci defines the remote router's local DLCI.
• broadcast specifies whether you want to forward broadcasts over the VC, permitting dynamic routing protocols over the VC.• ietf cisco is the encapsulation type.
What Cisco IOS command displays the LMI traffic statistics and LMI type?
The show frame-relay lmi command displays the LMI traffic statistics and LMI type:
RouterA#show frame-relay lmi
LMI Statistics for interface Serial0 (Frame Relay DTE)
LMI TYPE = CISCO Invalid Unnumbered info 0
Invalid Prot Disc 0 Invalid dummy Call Ref 0
Invalid Msg Type 0 Invalid Status Message 0
Invalid Lock Shift 0 Invalid Information ID 0
Invalid Report IE Len 0 Invalid Report Request 0
Invalid Keep IE Len 0 Num Status Enq. Rcvd 1748
Num Status msgs Sent 1748 Num Update Status Sent 0
Num St Enq. Timeouts 0
routera#
How do you display the current Frame Relay map entries and information about these connections on a Cisco router?
To view the current map entries and information about the connections, use the show frame-relay map command:
RouterA#show frame-relay map
Quick Notes - ROUTING
How do OSPF-enabled routers build adjacencies and exchange their routing tables?
OSPF-enabled routers build adjacencies by sending Hello packets out through all OSPF-enabled interfaces.
If these routers share a command link and agree on parameters set within their Hello packets then they become neighbors. If these parameters differ then the routers do not become neighbors and communication stops.
OSPF routers form adjacencies with certain routers. These routers are determined by the layer 2 (data link) media type and as soon as the adjacencies are formed each router sends LSAs (Link State Advertisements) to all adjacent routers. The LSAs describe the state of each router's links. There are multiple LSA types and a route that receives an LSA from a neighbor records the LSA in a link-state database and floods a copy of the LSA to all its other neighbors.
When all databases are complete - then each router uses the SPF (Shortest-Path First) algorithm to calculate a loop-free topology and builds its routing table based on this topology.
It is important to note that the Hello protocol is bidrectional and is the means by which neighbors are discovered and acts as keepalives between neighboring routers. It also establishes and maintain neighbor relationships and elects the DR (Designated Router) and BDR (Backup Designated Router) to represent the segment on Broadcast and NBMA (nobroadcast multiaccess) networks.
Note: Hello protocols are sent periodically sent out each OSPF-enabled interface using IP multicast address 224.0.0.5. The default interval on NBMA (nonbroadcast multiaccess) networks is 30 seconds. The default interval on Broadcast, Point-to-point, and point-to-multipoint networks is 10 seconds.
What are LSAs (link-state advertisements)?
LSAs are sent out all OSPF-enabled router interfaces describing the state of the router's links. They are also packets that OSPF uses to advertise changes in the condition of a link or other OSPF routers.
Name two LSA (link-state advertisement) types?
Type 1 LSAs are router LSAs and are generated by each router for the area to which the router belongs. These LSAs describe the states of the router'links to the area (area 0 for example) and are flooded within a single area (area 0 for example).
Type 2 LSAs are network LSAs and are generated by the DR (Designated Router) and the BDR (Backup Designated Router). They describe the routers attached to a particular network and are flooded within a single area (area 0 for example).
What is the routing metric OSPF is based on?
Bandwith.
Formula: Cost = 100,000,000 / bandwidth in bits per seconds
The cost of a 100 MBbps connection would be:
1000,000,000 / 100,000,000 =1
Based on the schema above -- if adjacencies are established with only with the DR (Designated Router) and BDR (Backup Designated Router)- what is the circuit count?
Formula:
2(n - 1) where n is the number of routers in the network.
2(5 - 1) = 8 circuits.
A circuit can also be thought of as an adjacency or connection.
Count four going into the DR and 4 going into the BDR for a total of 8.
Note: OSPF avoids synchronizing between every pair of routers in the network by using a DR and BDR. This way adjacencies are formed only to the DR and BDR, and the number of LSAs sent over the network is reduced. Now only the DR and BDR have four adjacencies, and all the other routers have two.
On an OSPF-enabled router -- what is the router ID and where does an OSPF-enabled router receive its router ID?
To initialize - OSPF must be able to define a router ID. The most common and stable source for a router ID is the IP address set on the logical loopback interface that is always available. If no logical interface is defined -- then the router receives its ID from the highest IP address on the physical interfaces.
Note: If two loopback addresses are defined -- it will use the highest loopback address. Think highest logical or highest physical interface address.
Name five OSPF network types:
Broadcast networks: Ethernet/Token Ring. OSPF-enabled routers on broadcast networks elect a DR (Designated Router) and BDR (Backup Designated Router). All the routers in the network form adjacencies with the DR and BDR. Note: OSPF packets are multicast to the DR and BDR.
NBMA (nonbroadcast multiaccess) networks: Frame Relay/X.25/ATM. NBMA networks can connect more than two routers but have no broadcast functionality. These networks elect an DR and BDR. Note: OSPF packets are unicast.
Point-to-point networks: A physical DS1 (T1) for example.
Point-to-point networks connect a pair of routers and always becomes adjacent.
Point-to-multipoint networks: Point-to-multipoint networks are a special configuration of NBMA networks in which networks are treated as a collection of point-to-point links. Point-to-multipoint networks do not elect a DR or BDR. Note: OSPF packets are multicast.
Virtual links: Virtual links area special configuration that the router interprets as unnumbered point-to-point networks. The network administrator creates/defines virtual links.
What is routing?
Routing is the process in which items are forwarded from one location to another. Routing is a hop-by-hop paradigm.
A Cisco router performs routing and switching functions. Describe what each function does.
Routing is a way to learn and maintain awareness of the network topology. Each router maintains a routing table in which it looks up the destination Layer 3 address to get the packet one step closer to its destination.
The switching function is the actual movement of temporary traffic through the router, from an inbound interface to an outbound interface.
What are the three types of routes you can use in a Cisco router?
The three types of routes are static routes, dynamic routes, and default routes.
What is the difference between static and dynamic routes?
Static routes are routes that an administrator manually enters into a router. Dynamic routes are routes that a router learns automatically through a routing protocol.
What is a default route?
Also known as the gateway of last resort, a default route is a special type of static route with an all-zeros network and network mask. The default route is used to route any packets to a network that a router does not directly know about to a next-hop router. By default, if a router receives a packet to a destination network that is not in its routing table, it drops the packet. When a default route is specified, the router does not drop the packet. Instead, it forwards the packet to the IP address specified in the default route.
What is a routing protocol?
A routing protocol defines the set of rules used by a router when it communicates with neighboring routers. Routing protocols listens for packets from other participants in order to learn and maintain a routing table.
What is administrative distance?
Administrative distance (AD) is an integer from 0 to 255 that rates the trustworthiness of routing information received on a router from a neighboring router. The AD is used as the tiebreaker when a router has multiple paths from different routing protocols to the same destination. The path with the lower AD is the one given priority.
What are the three classes of routing protocols?
1) Distance vector 2) Link-state 3) Balanced hybrid
What is the AD for each of the following?
Directly connected interface 0
Static route 1
EIGRP 90
IGRP 100
OSPF 110
RIP 120
External EIGRP 170
Unknown 255
How do distance vector routing protocols function?
Also known as Bellman-Ford-Fulkerson algorithms, distance vector routing protocols pass complete routing tables to neighboring routers. Neighboring routers then combine the received routing table with their own routing table. Each router receives a routing table from its directly connected neighbor. Distance vector routing tables include information about the total cost and the logical address of the first router on the path to each network they know about.
How do distance vector routing protocols keep track of any changes to the internetwork?
Distance vector routing protocols keep track of an internetwork by periodically broadcasting updates out all active interfaces. This broadcast contains the entire routing table. This method is often called routing by rumor.
Slow convergence of distance vector routing protocols can cause inconsistent routing tables and routing loops.
What are some mechanisms that distance vector protocols implement to prevent routing loops and inconsistent routing tables?
Here are some of the ways distance vector routing protocols prevent routing loops and inconsistent routing tables:
• Maximum hop count• Split horizon
• Route poisoning• Holddowns
What is split horizon?
The rule of split horizon is that it is never useful to send information about a route back in the direction from which the original update came.
What is convergence?
Convergence is when all routers have consistent knowledge and correct routing tables.
What is route poisoning?
With route poisoning, when a distance vector routing protocol notices that a route is no longer valid, the route is advertised with an infinite metric, signifying that the route is bad. In RIP, a metric of 16 is used to signify infinity. Route poisoning is used with holddowns.
What are hold-down timers?
Hold-down timers prevent regular update messages from reinstating a route that might have gone bad. Hold-down timers also tell routers to hold for a period of time any changes that might affect routes.
What are triggered updates?
When a router notices that a directly connected subnet has changed state, it immediately sends another routing update out its other interfaces rather than waiting for the routing update timer to expire. Triggered updates are also known as Flash updates.
What is IP RIP?
IP RIP is a true distance vector routing protocol that sends its complete routing table out all active interfaces every 30 seconds. IP RIP uses a hop count as its metric to determine the best path to a remote network. The maximum allowable hop count is 15, meaning that 16 is unreachable. There are two versions of RIP. Version 1 is classful, and version 2 is classless. IP RIP can load-balance over as many as six equal-cost paths.
What four timers does IP RIP use to regulate its performance?
Here are the four timers that IP RIP uses to regulate its performance: • Route update timer Time between router updates. The default is 30 seconds.• Route invalid timer Time that must expire before a route becomes invalid. The default is 180 seconds.• Route hold-down timer If IP RIP receives an update with a hop count higher than the metric recorded in the routing table, the router goes into holddown for 180 seconds.• Route flush timer Time from when a route becomes invalid to when it is removed from the routing table. The default is 240 seconds.
How do you stop RIP updates from propagating out an interface on a router?
Sometimes you do not want RIP updates to propagate across the WAN, wasting valuable bandwidth or giving out valuable information about your internetwork. The easiest way to stop RIP updates from propagating out an interface is to use the passive-interface global configuration command.
How do you display the contents of a Cisco IP routing table?
The show ip route command displays the Cisco routing table's contents.
What is Interior Gateway Routing Protocol (IGRP)?
IGRP is a Cisco proprietary distance vector routing protocol. IGRP has a default hop count of 100 hops, with a maximum hop count of 255. IGRP uses bandwidth and line delay as its default metric, but it can also use reliability, load, and MTU.
How do you enable IGRP on a Cisco router?
The way you enable IGRP on a Cisco router is similar to the way you enable RIP, except you specify IGRP as the protocol and add an autonomous system number. For example:
RouterA(config)#router igrp 10 (10 is the AS number)
RouterA(config-router)#network 192.168.0.0
RouterA(config-router)#network 192.168.1.0
RouterA(config-router)#network 192.168.2.0
What four timers does IGRP use to regulate its performance?
The four timers IGRP uses to regulate its performance are as follows:
• Route update timer Time between router updates The default is 90 seconds.
• Route invalid timer Time that must expire before a route becomes invalid . The default is 270 seconds.
• Route hold-down timer If a destination becomes unreachable, or if the next-hop router increases the metric recording in the routing table, the router goes into holddown for 280 seconds.
• Route flush timer[md]Time from when a route becomes invalid to when it is removed from the routing table. The default is 630 seconds.
Quick Notes - SWITCHING
What are three types of LAN traffic?
Unicasts - intended for one host.
Broadcasts - intended for everyone.
Multicasts - intended for a only a subset or group within an entire network.
What are unicast frames?
Unicast frames are the most common type of network traffic. A unicast frame is a frame intended for only one host. The only station that processes this frame is one station that has its own MAC address in the destination portion of packet.
What are broadcast frames?
Broadcast frames are frames intended for everyone. Stations view broadcast frames as public service announcements. All stations receive and process broadcast frames. In large networks, broadcasts can cause serious performance degradation in network hosts - (broadcast storm).
The destination address of broadcast frames (Data Link / Layer 2 broadcast addresses is FF-FF-FF-FF-FF-FF or alternatively all 1s in binary (11111111).
What are multicast frames?
Multicast frames address a group of devices that have a common interest. These frames allow the source to send only one copy of the frame on the network even though it is intended for several stations. Only stations that have a card that is configured by software to receive multicast frames for a particular multicast group can process a frame to that multicast address - all other stations discard multicast frames
What three major functions do Data Link Layer / Layer 2 Switches perform?
Address learning
Packet forwarding/filtering
Loop avoidance by spanning tree
What will occur when you attempt to segment a network with hubs and repeaters?
Basically, hubs and repeaters become extensions of the physical cable plant. All devices that connect to either a hub or a repeater share the same bandwidth and by definition hubs and repeaters create a single broadcast and collision domain.
Think of both devices are pass-through devices much like a electrical power-strip. Hubs and repeaters reside on the Physical Layer / Layer 1 of the OSI model where they pass 0s and 1s along the wire or up to the Data Link Layer. CSUs / Channel Service Units fall into the same category. All are regarded as unintelligent devices. No addressing takes place on the Physical layer.
What three devices are used to segment a LAN?
Router - logical addressing - IP address
Switch - physical addressing - MAC address
Bridge - physical addressing - MAC addres
What is microsegmentation?
Each workstation or network device on the network has its own dedicated segment - also known as a Collision Domain - to a switch. Each device gets the segments full bandwidth and does not have to share the dedicated segment with other devices. Collisions are reduced because each segment is its own Collision Domain.
Important: Full-duplex transmission is achieved by microsegmentation. Each device can send and receive at the same time which doubles the amount of bandwidth between nodes.
What are the three switching methods in Cisco Catalyst switches?
The three frame operating modes to handle frame switching are
Store-and-forward
Cut-through
Fragment-free
What is the Cisco Catalyst store-and-forward switching method?
In the store-and-forward switching method, the switch receives the entire frame before it forwards it. The switch reads the cyclic redundancy check (CRC) to make sure the frame is not bad. If the frame is good, the switch forwards it. Because the switch stores the frame before forwarding it, latency is introduced in the switch. Latency through the switch varies with the size of the frame.
What is the Cisco Catalyst cut-through switching method?
In cut-through switching mode, the switch only checks the frame's destination address and immediately begins forwarding the frame out the appropriate port. Because the switch checks the destination address in only the header and not the entire frame, the switch forwards a collision frame or a frame that has a bad CRC.
What is the Cisco Catalyst fragment-free switching method?
Also known as modified cut-through, fragment-free switching checks the first 64 bytes before forwarding the frame. Ethernet specifications state that collisions should be detected during the first 64 bytes of the frame. By reading the first 64 bytes of the frame, the switch can filter most collisions, although late collisions are still possible.
What is the default switching mode in Cisco Catalyst 1900 switches?
The default switching mode for the Catalyst 1900 is fragment-free.
What is half-duplex transmission mode?
Half-duplex transmission is the default mode that Ethernet functions in. In half-duplex transmission, a device can only send or receive--not do both at once. In half-duplex mode, stations are susceptible to collisions, and efficiency is rated at 50 to 60 percent.
What is full-duplex transmission mode?
In full-duplex mode, a station can send and receive at the same time. In full-duplex mode, collision detection is disabled. This mode offers 100 percent efficiency in both directions.
On a Cisco Catalyst 1900 switch, what are the default duplex settings for 10BaseT/100BaseT ports, default switching mode, and default protocols?
What are dynamic addresses on a Catalyst switch?
Dynamic addresses are addresses that the switch learns about dynamically through the learning process. If the switch does not see a MAC address for a certain amount of time, it drops the MAC address.
What are permanent MAC addresses on a Catalyst switch?
Permanent MAC addresses are entered manually by the administrator and are not aged out.
Quick Notes - Network Management
What is the Cisco Discovery Protocol (CDP)?
CDP is a Cisco proprietary protocol that runs on all Cisco IOS-enabled d
What is carrier sense multiple access collision detect (CSMA/CD)?
CSMA/CD describes the Ethernet access method. In CSMA/CD, many stations can transmit on the same cable, and no station has priority over any other. Before a station transmits, it listens on the wire to make sure no other station is transmitting. If no other station is transmitting, the station transmits across the wire. CSMA/CD is all about devices taking turns using the wire.
What are MAC addresses?
For computers to identify each other on the data link layer, they need a MAC address (hardware address). All devices on a LAN must have a unique MAC address. A MAC address is a 48-bit (six octet) address burned into a network interface card. The first three octets (24 bits) of the MAC address indicate the vendor that manufactured the card. This is called the Organization Unique Identifier (OUI). The last three octets of the MAC address are the unique host address. An example of a MAC address is 00-80-C6-E7-9C-EF.
What are the three types of LAN traffic?
The three types of LAN traffic are:
Unicasts
Broadcasts
Multicasts
What are unicast frames?
Unicast frames are the most common type of LAN traffic. A unicast frame is a frame intended for only one host. In unicast frames, the only station that processes the frame is the station that has its own MAC address in the destination portion of the packet.
What are broadcast frames?
Broadcast frames are frames intended for everyone. Stations view broadcast frames as public service announcements. All stations receive and process broadcast frames. In large networks, broadcasts can bring the network to a crawl, because every computer must process them.
What is the destination address of broadcast frames?
The destination address of broadcast frames (Layer 2 broadcast addresses) is FF-FF-FF-FF-FF-FF, or all 1s in binary.
What are multicast frames?
Multicast frames address a group of devices that have a common interest. These frames allow the source to send only one copy of the frame on the network even though it is intended for several stations. Only stations that have a card that is configured to receive multicast frames process them. All other stations discard multicast frames.
What devices can you use to segment a LAN at Layer 1, Layer 2, and Layer 3?
Three devices you can use to segment a LAN are:
Hubs/repeaters (Layer 1)
Bridges/switches (Layer 2) - physical addresses
Routers (Layer 3) - logical addresses
What happens when you segment the network with hubs/repeaters?
Because hubs and repeaters operate at the physical layer of the OSI model, segmenting a network with these devices appears as an extension to the physical cable. Hubs and repeaters are transparent to devices. They are unintelligent devices. All devices that connect to a hub/repeater share the same bandwidth. Hubs/repeaters create a single broadcast and collision domain.
What is the advantage of segmenting a network with bridges/switches?
Bridges/switches operate at Layer 2 of the OSI model and filter by MAC address. Each port on a bridge/switch provides full-dedicated bandwidth and creates a single collision domain. Because bridges/switches operate at Layer 2 of the OSI model, they cannot filter broadcasts, and they create a single broadcast domain. For the CCNA test, remember that switches create more collision domains and fewer collisions.
What is the difference between bridges and switches?
Bridges and switches function the same way; the only difference is in how they are implemented. Bridges are implemented by software and usually have a couple of network ports. Switches are implemented in hardware by ASIC chips and have many ports.
What are the advantages and disadvantages of segmenting the LAN with routers?
An advantage of segmenting the LAN with routers is that each interface on a router creates a single broadcast and collision domain. Routers operate at Layer 3 of the OSI model and do not propagate broadcasts. Some disadvantages are that routers are not transparent and are implemented in software, thus introducing latency in the network.
What is the Maximum Transmission Unit (MTU) for an Ethernet frame?
1500 bytes is the MTU for an Ethernet frame. You will notice that some publications state that the MTU for Ethernet is 1518 bytes. This is correct also. But what is the true answer? The MTU for Ethernet, including the header, source and destination address, data, and CRC is 1518 bytes. The MTU for the data portion of the frame is 1500 bytes.
What three major functions do Layer 2 switches provide?
The three major functions that Layer 2 switches provide are
Address learning
Packet forwarding/filtering
Loop avoidance by spanning tree
What are some advantages of switches?
Some advantages of switches are as follows:
They increase available network bandwidth.
They reduce the number of users per segment.
They provide dedicated bandwidth to each segment.
Transparent bridging (switching) provides five bridging functions to determine what to do when it receives a frame.
What are these five processes?
The five processes are:
Learning
Flooding
Filtering
Forwarding
Aging
In transparent bridging, what is the learning process?
The first process a bridge goes through when it is powered on is the learning process. The MAC address table on the bridge contains no entries, and the bridge goes through the learning process to record all workstations on every interface. In the learning process, the bridge records the source MAC address and source port number in the MAC address table every time it sees a frame.
In transparent bridging, what is the flooding process?
When a bridge is first turned on, it has no MAC address in its table. When a switch receives a unicast frame, it knows the source address and port from which the unicast frame came, but no entry exists in its table for the destination address. This is called an unknown unicast frame. When a switch receives an unknown unicast frame, it sends the frame out all forwarding interfaces on the bridge except the interface that received the frame. This process is the flooding process.
In transparent bridging, what is the filtering process?
The filtering process occurs when the source and destination addresses reside on the same interface on the bridge. Because the bridge does not need to forward a frame in which the destination and source addresses reside on the same interface, it filters the frame and discards it.
In transparent bridging, what is the forwarding process?
The forwarding process occurs when a switch receives a unicast frame and has an entry of the destination address in its MAC table. The switch then forwards the frame to the interface where that destination address resides.
In transparent bridging, what occurs during the aging process?
Every time a bridge learns a source address, it time-stamps the entry. When the bridge sees a frame from this source, it updates the time stamp. If the bridge does not hear from the source for a specific amount of time (called the aging timer), the bridge deletes the entry from its MAC address table. This process is the aging process.
What is the default aging time in transparent bridges?
The default aging timer is 5 minutes.
What is the Spanning-Tree Protocol (STP)?
STP is a loop-prevention bridge-to-bridge protocol. Its main purpose is to dynamically maintain a loop-free network. It does this by sending out Bridge Protocol Data Units (BPDUs), discovering any loops in the topology, and blocking one or more redundant links.
How does STP maintain a loop-free network?
STP maintains a loop-free network by
Electing a root bridge
Electing a root port on each nonroot bridge
Electing designated ports
Putting in the blocking state any port that is not a root port or designated port
In spanning tree, what is a Bridge ID (BID)?
A BID is an 8-byte field that is composed of the bridge's 6-byte MAC address and a 2-byte bridge priority.
What is the default bridge priority in a Bridge ID for all Cisco switches?
32,768
In spanning tree, what is path cost?
Path cost is a calculation to determine the link's bandwidth. It is a value assigned to each port that is based on the port's speed.
What is the spanning tree path cost for each of the following?
10 Mbps
100 Mbps
1 Gbps
The path costs are as follows:
10 Mbps - 100
100 Mbps - 19
1 Gbps - 4
When calculating a loop-free environment, what four-step decision sequence does spanning tree use to determine what will be the root bridge and which ports will forward or block?
The four-step decision sequence that spanning tree uses to determine the root bridge and which port will forward is as follows:
Step 1. The lowest root BID
Step 2. The lowest path cost to the root bridge
Step 3. The lowest sender BID
Step 4. The lowest port ID
How do bridges pass spanning tree information between themselves?
Bridges pass STP information using special frame called Bridge Protocol Data Units (BPDUs).
How often do bridges send BPDUs out active ports?
The default time that bridges send BPDUs out active ports is 2 seconds.
Note: All ports on a switch listen for BPDUs in case there is a topology change.
In STP, how is a root bridge elected?
In STP, the bridge with the lowest BID is elected the root bridge. All ports on the root bridge are placed in the forwarding state and are called designated ports.
Note: The BID is a 6-byte field that is composed of a default priority (32,768) and a MAC address. Because all Cisco switches use the default priority, the switch with the lowest MAC address is elected the root bridge. As a rule of thumb, lower will always win in spanning tree.
After bridges elect the root bridge, what do they do next?
After electing the root bridge, switches elect root ports. A root port is the port on nonroot bridges that is closest to the root bridge. Every nonroot bridge must select one root port.
How do nonroot bridges decide which port they will elect as a root port?
Nonroot bridges use root path cost to determine which port will be the root port. Root path cost is the cumulative cost of all links to the root bridge. The port with the lowest root path cost is elected the bridge's root port and is placed in the forwarding state.
What is the difference between path cost and root path cost?
Path cost is the value assigned to each port. It is added to BPDUs received on that port to calculate the root path cost. Root path cost is defined as the cumulative cost to the root bridge. In a BPDU, this is the value transmitted in the cost field. In a bridge, this value is calculated by adding the receiving port's path cost to the value contained in the BPDU.
If a nonroot bridge has two redundant ports with the same root path cost, how does the bridge choose which port will be the root port?
If a nonroot bridge has redundant ports with the same root path cost, the deciding factor is the port with the lowest port ID (port number).
After the root bridge and root ports are selected, the last step in spanning tree is to elect designated ports. How do bridges elect designated ports?
In spanning tree, each segment in a bridged network has one designated port. This port is a single port that both sends and receives traffic to and from that segment and the root bridge. All other ports are placed in a blocking state. This ensures that only one port on any segment can send and receive traffic to and from the root bridge, ensuring a loop-free topology. The bridge containing the designated port for a segment is called the designated bridge for that segment. Designated ports are chosen based on cumulative root path cost to the root bridge.
Note: Every active port on the root bridge becomes a designated port.
If a bridge is faced with a tie in electing designated ports, how does it decide which port will be the designated port?
In the event of a tie, STP uses the four-step decision process discussed in Question 30. It first looks for the BPDU with the lowest BID; this is always the root bridge. If the switch is not the root bridge, it moves to the next step: the BPDU with the lowest path cost to the root bridge. If both paths are equal, STP looks for the BPDU with the lowest sender BID. If these are equal, STP uses the link with the lowest port ID as the final tiebreaker.
What are the four spanning tree port states?
The four spanning tree port states are
Blocking
Listening
Learning
Forwarding
Remember that root and designated ports forward traffic and that nondesignated ports block traffic but still listen for BPDUs.
Important note: There is another port state - Disabled - (No frames forwarded, no BPDUs heard). If it shows up in the answer options - select it along with the others.
What is the STP blocking state?
When a switch starts, all ports are in the blocking state. This is to prevent any loops in the network. If there is a better path to the root bridge, the port remains in the blocked state. Ports in the blocked state cannot send or receive traffic, but they can receive BPDUs.
What is the STP listening state?
Ports transition from a blocked state to a listening state. In this state, no user data is passed. The port only listens for BPDUs. After listening for 15 seconds (if the bridge does not find a better path), the port moves to the next state, the learning state.
What is the STP learning state?
In the STP learning state, no user data is being passed. The port quietly builds its bridging table. The default time in the learning state is 15 seconds.
What is the STP forwarding state?
After the default time in the learning state is up, the port moves to the forwarding state. In the forwarding state, the port sends and receives data.
What is STP forward delay?
The forward delay is the time it takes for a port to move from the listening state to the learning state or from the learning state to the forwarding state. The default time is 30 seconds.
What is the hello time in STP timers?
The hello time is the time interval between the sending of BPDUs. The default time is 2 seconds.
What is the Max Age timer?
The Max Age timer is how long a bridge stores a BPDU before discarding it. The default time is 20 seconds (ten missed hello intervals).
What is the default time a port takes to transition from the blocking state to the forwarding state?
The default time a port takes to transition from the blocking state to the forwarding state is 50 seconds: 20 seconds for Max Age, 15 seconds for listening, and 15 seconds for learning.
What does STP do when it detects a topology change in the network due to a bridge or link failure?
If spanning tree detects a change in the network due to a bridge or link failure, at least one bridge interface changes from the blocking state to the forwarding state, or vice versa.
WAN
The three WAN connection types available are leased lines, circuit-switched, and packet-switched. Define the differences between each connection type.
Leased lines are dedicated point-to-point lines that provide a single preestablished WAN communication path from the customer's network to the remote network. Leased lines are usually employed over synchronous connections. They are generally expensive and are always up.
Circuit-switched connections are dedicated for only the duration of the call. The telephone system and ISDN are examples of circuit-switched networks. Packet-switched connections use virtual circuits (VCs) to provide end-to-end connectivity.
Packet-switched connections are similar to leased lines, except that the line is shared by other customers. A packet knows how to reach its destination by programming of switches. Frame Relay is an example of a packet-switched connection.
Define customer premises equipment (CPE), and give an example.
CPE is equipment that is located on the customer's (or subscriber's) premises. It is equipment owned by the customer or equipment leased by the service provider to the customer. An example is your router.
What is the demarcation point (demarc)?
The demarc is the point where the CPE ends and the local loop begins. It is the last responsibility of the service provider and is usually an RJ-45 jack located close to the CPE. Think of the demarc as the boundary between the customer's wiring and the service provider's wiring.
What is the local loop?
The local loop is the physical cable that extends from the demarc to the central office.
Describe the central office (CO).
The CO is the telco switching facility that connects the customer to the provider's switching network. The CO is sometimes referred to as a point of presence. It is the point where the local loop gains access to the service provider's access lines.
What is the toll network?
All the telco switches, COs, and trunk lines inside the WAN provider's network are the toll network.
What are synchronous links?
Synchronous links have identical frequencies and contain individual characters encapsulated in control bits, called start/stop bits, that designate the beginning and end of each character. Synchronous links try to use the same speed as the other end of a serial link.
What are Asynchronous links?
Asynchronous links send digital signals without timing. Asynchronous links agree on the same speed, but there is no check or adjustment of the rates if they are slightly different. Only 1 byte per transfer is sent.
List some typical Layer 2 encapsulation methods for WAN links.
. High-Level Data Link Control (HDLC)
• Point-to-Point Protocol (PPP)
• Serial Line Internet Protocol (SLIP)
• X.25/Link Access Procedure, Balanced (LAPB)
• Frame Relay• Asynchronous Transfer Mode (ATM)
Describe HDLC.
HDLC was derived from Synchronous Data Link Control (SDLC). It is the default encapsulation type on point-to-point dedicated links and circuit-switched connections between Cisco routers. It is an ISO-standard bit-oriented data-link protocol that encapsulates data on synchronous links. HDLC is a connection-oriented protocol that has very little overhead. HDLC lacks a protocol field and therefore cannot encapsulate multiple network layer protocols across the same link. Because of this, each vendor has its own method of identifying the network-layer protocol. Cisco offers a propriety version of HDLC that uses a type field that acts as a protocol field, making it possible for multiple network-layer protocols to share the same link.
By default, Cisco uses HDLC as its default encapsulation method across synchronous lines (point-to-point links). If a serial line uses a different encapsulation protocol, how do you change it back to HDLC?
To change a serial line back to HDLC, use the following interface command on the serial interface you want to change: Router(config-if)#encapsulation hdlc
What is the Point-to-Point Protocol (PPP)?
PPP is an industry-standard protocol that provides router-to-router or router-to-host connections over synchronous and asynchronous links. It can be used to connect to other vendors' equipment. It works with several network-layer protocols, such as IP and IPX. PPP provides authentication through PAP or CHAP.
Describe X.25/LAPB.
X.25/LAPB is an ITU-T standard that has a tremendous amount of overhead because of its strict timeout and windowing techniques. LAPB is the connection-oriented protocol used with X.25. It uses the ABM (Asynchronous Balance Mode) transfer mode. X.25/LAPB was used in the 1980s when WAN links were not as error-free as they are today. X.25 is a predecessor of Frame Relay. X.25 supports both switched and permanent virtual circuits.
What is Frame Relay?
An industry standard, Frame Relay is a switched data link layer protocol that uses virtual circuits to identify the traffic that belongs to certain routers. It provides dynamic bandwidth allocation and congestion control.
Quick Notes - INTERNETWORKING
What are the three layers of the Cisco Hierarchical Model?
The three layers of the Cisco Hierarchical Model are: 1
the access layer
The distribution layer
The core layer
In the Cisco Hierarchical Model, what is the function of the access layer?
Sometimes referred to as the desktop layer, the access layer is the point at which users connect to the network through low-end switches. Some functions of the access layer include:
Connectivity into the distribution layer
Shared Bandwidth
MAC Address filtering (switching)
Segmentation
What is the function of the distribution layer in the Cisco Hierarchical Model?
The distribution layer is also known as the workgroup layer. It is the demarcation point between the access and core layers of the network. Its primary function is to provide routing, filtering, and WAN access. The distribution layer determines how packets access the core, so it is the layer at which to implement policy-based connectivity. Some functions include the following:
Collection point for access layer devices
Broadcast and multicast domain segmentation
Security and filtering services such as firewalls and access lists
Providing translation between different media types
Inter-VLAN routing
What is the role of the core layer in the Cisco Hierarchical Model?
The core layer is the backbone of the network. Its main function is to switch traffic as fast as possible. Therefore, it should not perform any filtering to slow down traffic.
The ISO's OSI Reference Model contains seven layers. What are they? Include the layer number and name of each layer in your answer.
The seven layers of the OSI model are as follows:
Layer 7 - Application layer
Layer 6 - Presentation layer
Layer 5 - Session layer
Layer 4 - Transport layer
Layer 3 - Network layer
Layer 2 - Data link layer
Layer 1 - Physical layer
What are some reasons that the industry uses a layered model?
Here are some reasons why the industry uses a layered model:
It encourages industry standardization by defining what functions occur at each level.
It allows vendors to modify or improve components at only one layer versus rewriting the whole protocol stack.
It helps interoperability by defining standards for the operations at each level.
It helps with troubleshooting.
What does the application layer (Layer 7) of the OSI model do, and what are some examples of this layer?
The application layer is the layer that is closest to the user. This means that this layer interacts directly with the software application. The application layer's main function is to identify and establish communication partners, determine resource availability, and synchronize communication. Some examples include the following:
TCP/IP applications such as Telnet, File Transfer Protocol (FTP), Simple Mail Transfer Protocol (SMTP), WWW, and HTTP.
OSI applications such as Virtual Terminal Protocol, File
Transfer, Access, and Management (FTAM), and Common Management Information Protocol (CMIP).
In the OSI model, what are the responsibilities of the presentation layer (Layer 6)? Give some examples of this layer.
Also known as the translator, the presentation layer provides coding and conversion functions to application layer data. This guarantees that the application layer on another system can read data transferred from the application layer of a different system. Some examples of the presentation layer are:
Compression, decompression, and encryption
JPEG, TIFF, GIFF, PICT, QuickTime, MPEG, and ASCII
What are the functions of the session layer (Layer 5)? Give some examples.
The session layer is responsible for creating, managing, and ending communication sessions between presentation layer entities. These sessions consist of service requests and responses that develop between applications located on different network devices. Some examples include SQL, RPC, NFS, X Window System, ZIP, NetBIOS names, and AppleTalk ASP.
What is the transport layer (Layer 4) responsible for? Give some examples of transport layer implementations.
The transport layer segments and reassembles data from upper-layer applications into data streams. It provides reliable data transmission to upper layers. End-to-end communications, flow control, multiplexing, error detection and correction, and virtual circuit management are typical transport layer functions. Some examples include TCP, UDP*, and SPX.
Note: watch out for end-to-end on communications on the exam! Transport layer.
* Error correction does not apply to UDP - connection-less - unreliable.....
What is flow control, and what are the three methods of implementing it?
Flow control is the method of controlling the rate at which a computer sends data, thus preventing network congestion. The three methods of implementing flow control are
Buffering
Congestion avoidance
Windowing
Almost certain to be on the exam.
Describe the function of the network layer (Layer 3), and give some examples of network layer implementations.
The network layer provides internetwork routing and logical network addresses. It defines how to transport traffic between devices that are not locally attached. The network layer also supports connection-oriented and connectionless service from higher-layer protocols. Routers operate at the network layer. IP, IPX, AppleTalk, and DDP are examples of network layer implementations.
Are network layer addresses physical or logical?
Network layer addresses are logical addresses specific to the network layer protocol being run on the network. Each network layer protocol has a different addressing scheme. They are usually hierarchical and define networks first and then host or devices on that network. An example of a network address is an IP address, which is a 32-bit address often expressed in decimal format. 192.168.0.1 is an example of an IP address in decimal format.
How do routers function at the network layer of the OSI model?
Routers learn, record, and maintain awareness of different networks. They decide the best path to these networks and maintain this information in a routing table. The routing table includes the following:
Network addresses, which are protocol-specific. If you are running more than one protocol, you have a network address for each protocol.
The interface the router uses to route a packet to a different network.
A metric, which is the distance to a remote network or the weight of the bandwidth, load, delay, and reliability of the path to the remote network.
Routers create broadcast domains. One interface on a router creates a single broadcast domain and collision domain. However, an interface on a switch creates only a single collision domain.
In addition to learning the remote network and providing a path to the network, what other functions do routers carry out?
Routers perform these tasks:
Routers, by default, do not forward broadcasts or multicasts.
Routers can perform bridging and routing functions.
If a router has multiple paths to a destination, it can determine the best path to the destination.
Routers forward traffic based on Layer 3 destination addresses.
Routers can connect Virtual LANs (VLANs).
Routers can provide quality of service for specified types of network traffic.
What is the responsibility of the data link layer (Layer 2)?
The data link layer provides functional and procedural means for connectionless mode among network entities, and for connection mode entities it provides the establishment, maintenance, and release of data link connections among network entities and for the transfer of data link service data units. The data link layer translates messages from the network layer into bits for the physical layer, and it enables the network layer to control the interconnection of data circuits within the physical layer. Its specifications define different network and protocol characteristics, including physical addressing, error notification, network topology, and sequencing of frames. Data link protocols provide the delivery across individual links and are concerned with the different media types, such as 802.2 and 802.3. The data link layer is responsible for putting 1s and 0s into a logical group. These 1s and 0s are then put on the physical wire. Some examples of data link layer implementations are IEEE 802.2/802.3, IEEE 802.5/802.2, packet trailer (for Ethernet, the FCS or CRC), FFDI, HDLC, and Frame Relay.
The IEEE defines what two sublayers of the data link layer?
The two sublayers of the data link layer are
The Logical Link Control (LLC) sublayer
The Media Access Control (MAC) sublayer
These two sublayers provide physical media independence.
For what is the LLC sublayer responsible?
The Logical Link Control (802.2) sublayer is responsible for identifying different network layer protocols and then encapsulating them to be transferred across the network. An LLC header tells the data link layer what to do with a packet after it is received.
What functions does the Media Access Control (MAC) sublayer provide?
The MAC sublayer specifies how data is placed and transported over the physical wire. The LLC layer communicates with the network layer, but the MAC layer communicates downward directly to the physical layer. Physical addressing (MAC addresses), network topologies, error notification, and delivery of frames are defined at this sublayer.
What are some network devices that operate at the data link layer?
Bridges and switches are network devices that operate at the data link layer. Both devices filter traffic by MAC addresses.
What is the function of the OSI model's physical layer (Layer 1)? Give some examples of physical layer implementations.
The physical layer defines the physical medium. It defines the media type, the connector type, and the signaling type (baseband versus broadband). This includes voltage levels, physical data rates, and maximum cable lengths. The physical layer is responsible for converting frames into electronic bits of data, which are then sent or received across the physical medium. Twisted pair, coaxial cable, and fiber-optic cable operate at this level. Other implementations at this layer are repeaters/hubs, RJ-45.
The Ethernet and IEEE 802.3 standards define what three physical wiring standards that operate at 10 Mbps?
These physical wiring standards operate at 10 Mbps:
10Base2
10Base5
10BaseT
What are collision domains?
In Ethernet segments, devices connect to the same physical medium. Because of this, all devices receive all signals sent across the wire. If two devices send a packet at the same time, a collision occurs. In the event of a collision, the two devices run a backoff algorithm and resend the packet. The devices retransmit up to 15 times. The first station to detect a collision issues a jam signal. When a jam signal is sent from a workstation, it affects all of the machines on the segment, not just the two that collided; when the jam signal is on the wire, no workstations can transmit data. The more collisions that occur in a network, the slower it will be, because the devices will have to resend the packet. A collision domain defines a group of devices connected to the same physical medium.
What are broadcast domains?
A broadcast domain defines a group of devices that receive each others' broadcast messages. As with collisions, the more broadcasts that occur on the network, the slower your network will be. This is because every device that receives a broadcast must process it to see if the broadcast is intended for it.
What devices are used to break up collision and broadcast domains?
Switches and bridges are used to break up collision domains. They create more collision domains and fewer collisions. Routers are used to break up broadcast domains. They create more broadcast domains and smaller broadcast areas.
How do the different layers of the OSI model communicate with each other?
Each layer of the OSI model can communicate only with the layer above it, below it, and parallel to it (a peer layer). For example, the presentation layer can communicate with only the application layer, session layer, and presentation layer on the machine it is communicating with. These layers communicate with each other using protocol data units (PDUs). These PDUs control information that is added to the user data at each layer of the model. This information resides in fields called headers (the front of the data field) and trailers (the end of the data field).
What is data encapsulation?
A PDU can include different information as it goes up or down the OSI model. It is given a different name according to the information it is carrying (the layer it is at). When the transport layer receives upper layer data, it adds a TCP header to the data; this is called a segment. The segment is then passed to the network layer, and an IP header is added; thus, the data becomes a packet. The packet is passed to the data link layer, thus becoming a frame. This frame is then converted into bits and is passed across the network medium. This is data encapsulationApplication layer -- Data
Transport layer -- Segment
Network layer -- Packet
Data link layer -- Frame
There is also the Physical Layer -- Bits
What is the difference between a routing protocol and a routed protocol?
Routing protocols determine how to route traffic to the best location of a routed protocol. Examples of routing protocols are RIP, EIGRP, OSFP, and BGP. Examples of routed protocols are IP and IPX.
What 3 devices are used to segment a LAN?
Router
Switch
Bridge
Quick Notes - CABLING TECHNOLOGY
What is a straight-through cable, and when would you use it?
A straight-through cable is the same at both ends. A straight-through cable uses pins 1, 2, 3, and 6. The send and receive wires are not crossed. You should use a straight-through cable when connecting dissimilar devices. Examples include connecting PCs to switches or hubs or a router to a switch or a hub.
What is a crossover cable, and when would you use it?
A crossover cable is a cable that has the send and receive wires crossed at one of the ends. On a Category 5 cable, the 1 and 3 wires and the 2 and 6 wires are switched on one of the cable's ends. You should use a crossover cable when connecting similar devices, such as connecting a router to a router, a switch to a switch or hub, a hub to a hub, or a PC to a PC.
Important tip -- Router (think of it as a PC) to PC via 10BaseT (NIC) uses a "crossover cable". (contradicts the rule)
How do you set up a console session to a Cisco device?
To set up a console session to a Cisco device, you connect a rollover cable to the console port on the Cisco device. You then connect the other end to your PC and configure a terminal emulation application to the following com settings: 9600 bps, 8 data bits, no parity, 1 stop bit, and no flow control.
What is the maximum cable length for each of the following?
The maximum cable lengths are as follows:
10Base2 (thinnet) 185 meters
10Base5 (thicknet) 500 meters
10BaseT 100 meters
10BaseFL 2000 meters (400 meters in a shared environment and 2000 meters in a point-to-point environment)
100BaseT 100 meters
What does Base stand for in 10BaseT and 100BaseT?
Base in 10BaseT and 100BaseT stands for baseband. Baseband is a network technology in which only one carrier frequency (signal) is used.
What is the difference between baseband and broadband?
Baseband is a network technology in which only one carrier frequency is used (such as Ethernet). Broadband is a network technology in which several independent channels are multiplexed into one cable (for example, a T1 line).
Quick Notes - ACCESS LISTS
Besides named access lists, what are the two types of IP access lists?
The two types of IP access lists are standard and extended.
What criteria do standard IP access lists use to filter packets?
Standard IP access lists filter packets by the source address. This results in the packet's being permitted or denied for the entire protocol suite based on the source network IP address.
What criteria do extended IP access lists use to filter packets?
Extended IP access lists filter packets by source address, destination address, protocols, and port numbers.
In what two ways can IP access lists be applied to an interface?
Access lists can be applied as inbound or outbound access lists. Inbound access lists process packets as they enter a router's interface and before they are routed. Outbound access lists process packets as they exit a router's interface and after they are routed.
How many access lists can be applied to an interface on a Cisco router?
Only one access list per protocol, per direction, per interface can be applied on a Cisco router. Multiple access lists are permitted per interface, but they must be for a different protocol.
How are access lists processed?
Access lists are processed in sequential, logical order, evaluating packets from the top down, one statement at a time. As soon as a match is made, the permit or deny option is applied, and the packet is not applied to any more access list statements. Because of this, the order of the statements within any access list is significant.
What is at the end of each access list?
At the end of each access list, an implicit deny statement denies any packet not filtered in the access list.
What are the number ranges used to define standard and extended IP access lists?
The number ranges used to define standard and extended IP access lists are as follows:
• Standard IP access lists 1 to 99 and 1300 to 1999• Extended IP access lists 100 to 199 and 2000 to 2699
When implementing access lists, what are wildcard masks?
Wildcard masks define the subset of the 32 bits in the IP address that must be matched. Wildcards are used with access lists to specify a host, network, or part of a network. Wildcard masks work exactly the opposite of subnet masks. In subnet masks, 1 bits are matched to the network portion of the address, and 0s are wildcards that specify the host range. In wildcard masks, when 0s are present, the octet address must match.
What is the IOS command syntax used to create a standard IP access list?
Here is the command syntax to create a standard IP access list:
access-list access-list-number {permit deny} source-address [wildcard mask]access-list-number is a number from 1 to 99.
For example:
RouterA(config)#access-list 10 deny 192.168.0.0 0.0.0.255
How can you display all access lists on a Cisco router?
To display all access lists on a Cisco router, use the show access-list command: RouterA#show access-list Standard IP access list 10 deny 192.168.0.0, wildcard bits 0.0.0.255Extended IP access list 101 permit tcp any any eq www permit udp any any eq domain permit udp any eq domain any permit icmp any any deny tcp 192.168.10.0 0.0.0.255 any eq wwwRouterA#
Quick Notes - FRAME RELAY
What protocol does Frame Relay rely on for error checking?
Frame Relay does not rely on any certain protocol for error checking. Instead, it relies on upper-layer protocols to provide error checking. For example, Frame Relay relies on TCP to provide error checking in an IP network.
At what layers of the OSI model does Frame Relay operate?
Frame Relay operates at the two lower layers of the OSI model (data link and physical).
What is the difference between switched virtual circuits (SVCs) and permanent virtual circuits (PVCs)?
SVCs are virtual circuits that are dynamically established when data needs to be transferred and that are terminated when data transmission is complete. SVCs consist of four states: call setup, data transfer, idle, and call termination. PVCs are permanently established virtual circuits that operate in one of two states: idle or data transfer. When the PVC is idle, the connection between the DTE devices is still active.
What is a Data Link Connection Identifier (DLCI)?
A DLCI is a number that identifies the logical circuit between the router and the Frame Relay switch. It is the Frame Relay Layer 2 address. The Frame Relay switch maps DLCIs between each pair of routers to create a PVC. For IP devices at the end of each virtual circuit to communicate, their IP addresses need to be mapped to DLCIs. If you are running Cisco IOS 11.2 or later, mapping is done automatically using Inverse ARP. DLCIs have local significance. Think of DLCIs as the MAC address of the Frame Relay network.
What is the committed information rate (CIR)?
The CIR is the committed information rate, by the service provider, in bits per second, at which data will be transferred. The service provider sends any data in excess of this rate if its network has capacity at that time.
How does Frame Relay use Inverse ARP?
Frame Relay uses Inverse ARP as a way to dynamically map a network layer address to a DLCI. With Inverse ARP, the router can discover the network address of a device associated with a VC.
What is the Local Management Interface (LMI)?
The LMI is a signaling standard between a CPE device (a router) and the Frame Relay switch that is responsible for managing and maintaining status between the devices. It is autosensed with Cisco IOS Release 11.2 and later.
In Frame Relay, what is Forward Explicit Congestion Notification (FECN)?
The FECN is the bit in the Frame Relay header that signals to anyone receiving the frame (switches and DTEs) that congestion is occurring in the same direction as the frame. Switches and DTEs can react by slowing the rate at which data is sent in that direction.
What is Backward Explicit Congestion Notification (BECN)?
The BECN is the bit in the Frame Relay header that signals to switches and DTEs receiving the frame that congestion is occurring in the direction opposite (backward) that of the frame. If switches and DTE devices detect that the BECN bit in the Frame Relay header is set to 1, they slow the rate at which data is sent in that direction.
In the Frame Relay header, what is the discard eligibility (DE) bit?
If congestion is detected on the Frame Relay network, the DE bit is turned on in the Frame Relay header. The DE bit is turned on for frames that are in excess of the CIR. The DE bit tells a switch which frames to discard if they must be discarded.
What is the default LMI type for Cisco routers that are configured for Frame Relay?
The default LMI for Cisco routers configured for Frame Relay is Cisco. If you are running Cisco IOS Release 11.2 or later, the Cisco router tries to autosense which LMI type the Frame Relay switch is using. If it cannot autosense the LMI type, the router uses Cisco as its LMI type. The three types of LMIs supported by Cisco routers are:
Cisco
ANSI
Q933a
When a router receives LMI information, it updates its VC status to one of three states. What are these three states?
The three states that a VC uses to update its status are as follows:
Active state The connection is active, and routers can exchange data.
Inactive state The local connection to the Frame Relay switch is working, but the remote router's connection to the Frame Relay switch is not working.
Deleted state Indicates that no LMIs are being received from the Frame Relay switch or that there is no service between the router and the Frame Relay switch.
How do you enable Frame Relay on a Cisco router?
To enable Frame Relay on a Cisco router, you must first enable the serial interface for Frame Relay encapsulation with the encapsulation frame-relay interface command:
RouterB(config)#int s 0
RouterB(config-if)#ip address 192.168.1.1 255.255.255.0
RouterB(config-if)#encapsulation frame-relay
The default encapsulation for a serial interface configured for Frame Relay is cisco. If you are connecting to a non-Cisco router, how do you change the encapsulation type?
If you are connecting to a non-Cisco router in a Frame Relay network, you need to specify ietf as the encapsulation type:
RouterB(config-if)#ip address 192.168.1.1 255.255.255.0
RouterB(config-if)#encapsulation frame-relay ietf
If you are using Cisco IOS Release 11.1 or earlier, or if you do not want to autosense the LMI type, how do you define the LMI type on a Cisco router?
To define the LMI type on a Cisco router, use the frame-relay lmi-type {ansi cisco q933a} interface command:
RouterB(config-if)#ip address 192.168.1.1 255.255.255.0
RouterB(config-if)#encapsulation frame-relay
RouterB(config-if)#frame-relay lmi-type ansi
If Inverse ARP is disabled on your router, how do you reenable it?
Inverse ARP is enabled by default on a Cisco router. If it is disabled, reenable it by using the following command:
RouterB(config-if)#frame-relay inverse-arp [protocol] [dlci]
Supported protocols indicated by the protocol option include ip, ipx, decnet, appletalk, vines, and xns.
If a remote router does not support Inverse ARP, you must define the address-to-DLCI table
statically. How do you create these static maps?
To define static maps on a Cisco router, use the following command:
RouterA(config-if)#frame-relay map protocol protocol-address dlci [broadcast] [ietf cisco] [payload-compress packet-by-packet]
where:
• protocol defines the supported protocol bridging or LLC.
• protocol-address is the remote router's network layer address.
• dlci defines the remote router's local DLCI.
• broadcast specifies whether you want to forward broadcasts over the VC, permitting dynamic routing protocols over the VC.• ietf cisco is the encapsulation type.
What Cisco IOS command displays the LMI traffic statistics and LMI type?
The show frame-relay lmi command displays the LMI traffic statistics and LMI type:
RouterA#show frame-relay lmi
LMI Statistics for interface Serial0 (Frame Relay DTE)
LMI TYPE = CISCO Invalid Unnumbered info 0
Invalid Prot Disc 0 Invalid dummy Call Ref 0
Invalid Msg Type 0 Invalid Status Message 0
Invalid Lock Shift 0 Invalid Information ID 0
Invalid Report IE Len 0 Invalid Report Request 0
Invalid Keep IE Len 0 Num Status Enq. Rcvd 1748
Num Status msgs Sent 1748 Num Update Status Sent 0
Num St Enq. Timeouts 0
routera#
How do you display the current Frame Relay map entries and information about these connections on a Cisco router?
To view the current map entries and information about the connections, use the show frame-relay map command:
RouterA#show frame-relay map
Quick Notes - ROUTING
How do OSPF-enabled routers build adjacencies and exchange their routing tables?
OSPF-enabled routers build adjacencies by sending Hello packets out through all OSPF-enabled interfaces.
If these routers share a command link and agree on parameters set within their Hello packets then they become neighbors. If these parameters differ then the routers do not become neighbors and communication stops.
OSPF routers form adjacencies with certain routers. These routers are determined by the layer 2 (data link) media type and as soon as the adjacencies are formed each router sends LSAs (Link State Advertisements) to all adjacent routers. The LSAs describe the state of each router's links. There are multiple LSA types and a route that receives an LSA from a neighbor records the LSA in a link-state database and floods a copy of the LSA to all its other neighbors.
When all databases are complete - then each router uses the SPF (Shortest-Path First) algorithm to calculate a loop-free topology and builds its routing table based on this topology.
It is important to note that the Hello protocol is bidrectional and is the means by which neighbors are discovered and acts as keepalives between neighboring routers. It also establishes and maintain neighbor relationships and elects the DR (Designated Router) and BDR (Backup Designated Router) to represent the segment on Broadcast and NBMA (nobroadcast multiaccess) networks.
Note: Hello protocols are sent periodically sent out each OSPF-enabled interface using IP multicast address 224.0.0.5. The default interval on NBMA (nonbroadcast multiaccess) networks is 30 seconds. The default interval on Broadcast, Point-to-point, and point-to-multipoint networks is 10 seconds.
What are LSAs (link-state advertisements)?
LSAs are sent out all OSPF-enabled router interfaces describing the state of the router's links. They are also packets that OSPF uses to advertise changes in the condition of a link or other OSPF routers.
Name two LSA (link-state advertisement) types?
Type 1 LSAs are router LSAs and are generated by each router for the area to which the router belongs. These LSAs describe the states of the router'links to the area (area 0 for example) and are flooded within a single area (area 0 for example).
Type 2 LSAs are network LSAs and are generated by the DR (Designated Router) and the BDR (Backup Designated Router). They describe the routers attached to a particular network and are flooded within a single area (area 0 for example).
What is the routing metric OSPF is based on?
Bandwith.
Formula: Cost = 100,000,000 / bandwidth in bits per seconds
The cost of a 100 MBbps connection would be:
1000,000,000 / 100,000,000 =1
Based on the schema above -- if adjacencies are established with only with the DR (Designated Router) and BDR (Backup Designated Router)- what is the circuit count?
Formula:
2(n - 1) where n is the number of routers in the network.
2(5 - 1) = 8 circuits.
A circuit can also be thought of as an adjacency or connection.
Count four going into the DR and 4 going into the BDR for a total of 8.
Note: OSPF avoids synchronizing between every pair of routers in the network by using a DR and BDR. This way adjacencies are formed only to the DR and BDR, and the number of LSAs sent over the network is reduced. Now only the DR and BDR have four adjacencies, and all the other routers have two.
On an OSPF-enabled router -- what is the router ID and where does an OSPF-enabled router receive its router ID?
To initialize - OSPF must be able to define a router ID. The most common and stable source for a router ID is the IP address set on the logical loopback interface that is always available. If no logical interface is defined -- then the router receives its ID from the highest IP address on the physical interfaces.
Note: If two loopback addresses are defined -- it will use the highest loopback address. Think highest logical or highest physical interface address.
Name five OSPF network types:
Broadcast networks: Ethernet/Token Ring. OSPF-enabled routers on broadcast networks elect a DR (Designated Router) and BDR (Backup Designated Router). All the routers in the network form adjacencies with the DR and BDR. Note: OSPF packets are multicast to the DR and BDR.
NBMA (nonbroadcast multiaccess) networks: Frame Relay/X.25/ATM. NBMA networks can connect more than two routers but have no broadcast functionality. These networks elect an DR and BDR. Note: OSPF packets are unicast.
Point-to-point networks: A physical DS1 (T1) for example.
Point-to-point networks connect a pair of routers and always becomes adjacent.
Point-to-multipoint networks: Point-to-multipoint networks are a special configuration of NBMA networks in which networks are treated as a collection of point-to-point links. Point-to-multipoint networks do not elect a DR or BDR. Note: OSPF packets are multicast.
Virtual links: Virtual links area special configuration that the router interprets as unnumbered point-to-point networks. The network administrator creates/defines virtual links.
What is routing?
Routing is the process in which items are forwarded from one location to another. Routing is a hop-by-hop paradigm.
A Cisco router performs routing and switching functions. Describe what each function does.
Routing is a way to learn and maintain awareness of the network topology. Each router maintains a routing table in which it looks up the destination Layer 3 address to get the packet one step closer to its destination.
The switching function is the actual movement of temporary traffic through the router, from an inbound interface to an outbound interface.
What are the three types of routes you can use in a Cisco router?
The three types of routes are static routes, dynamic routes, and default routes.
What is the difference between static and dynamic routes?
Static routes are routes that an administrator manually enters into a router. Dynamic routes are routes that a router learns automatically through a routing protocol.
What is a default route?
Also known as the gateway of last resort, a default route is a special type of static route with an all-zeros network and network mask. The default route is used to route any packets to a network that a router does not directly know about to a next-hop router. By default, if a router receives a packet to a destination network that is not in its routing table, it drops the packet. When a default route is specified, the router does not drop the packet. Instead, it forwards the packet to the IP address specified in the default route.
What is a routing protocol?
A routing protocol defines the set of rules used by a router when it communicates with neighboring routers. Routing protocols listens for packets from other participants in order to learn and maintain a routing table.
What is administrative distance?
Administrative distance (AD) is an integer from 0 to 255 that rates the trustworthiness of routing information received on a router from a neighboring router. The AD is used as the tiebreaker when a router has multiple paths from different routing protocols to the same destination. The path with the lower AD is the one given priority.
What are the three classes of routing protocols?
1) Distance vector 2) Link-state 3) Balanced hybrid
What is the AD for each of the following?
Directly connected interface 0
Static route 1
EIGRP 90
IGRP 100
OSPF 110
RIP 120
External EIGRP 170
Unknown 255
How do distance vector routing protocols function?
Also known as Bellman-Ford-Fulkerson algorithms, distance vector routing protocols pass complete routing tables to neighboring routers. Neighboring routers then combine the received routing table with their own routing table. Each router receives a routing table from its directly connected neighbor. Distance vector routing tables include information about the total cost and the logical address of the first router on the path to each network they know about.
How do distance vector routing protocols keep track of any changes to the internetwork?
Distance vector routing protocols keep track of an internetwork by periodically broadcasting updates out all active interfaces. This broadcast contains the entire routing table. This method is often called routing by rumor.
Slow convergence of distance vector routing protocols can cause inconsistent routing tables and routing loops.
What are some mechanisms that distance vector protocols implement to prevent routing loops and inconsistent routing tables?
Here are some of the ways distance vector routing protocols prevent routing loops and inconsistent routing tables:
• Maximum hop count• Split horizon
• Route poisoning• Holddowns
What is split horizon?
The rule of split horizon is that it is never useful to send information about a route back in the direction from which the original update came.
What is convergence?
Convergence is when all routers have consistent knowledge and correct routing tables.
What is route poisoning?
With route poisoning, when a distance vector routing protocol notices that a route is no longer valid, the route is advertised with an infinite metric, signifying that the route is bad. In RIP, a metric of 16 is used to signify infinity. Route poisoning is used with holddowns.
What are hold-down timers?
Hold-down timers prevent regular update messages from reinstating a route that might have gone bad. Hold-down timers also tell routers to hold for a period of time any changes that might affect routes.
What are triggered updates?
When a router notices that a directly connected subnet has changed state, it immediately sends another routing update out its other interfaces rather than waiting for the routing update timer to expire. Triggered updates are also known as Flash updates.
What is IP RIP?
IP RIP is a true distance vector routing protocol that sends its complete routing table out all active interfaces every 30 seconds. IP RIP uses a hop count as its metric to determine the best path to a remote network. The maximum allowable hop count is 15, meaning that 16 is unreachable. There are two versions of RIP. Version 1 is classful, and version 2 is classless. IP RIP can load-balance over as many as six equal-cost paths.
What four timers does IP RIP use to regulate its performance?
Here are the four timers that IP RIP uses to regulate its performance: • Route update timer Time between router updates. The default is 30 seconds.• Route invalid timer Time that must expire before a route becomes invalid. The default is 180 seconds.• Route hold-down timer If IP RIP receives an update with a hop count higher than the metric recorded in the routing table, the router goes into holddown for 180 seconds.• Route flush timer Time from when a route becomes invalid to when it is removed from the routing table. The default is 240 seconds.
How do you stop RIP updates from propagating out an interface on a router?
Sometimes you do not want RIP updates to propagate across the WAN, wasting valuable bandwidth or giving out valuable information about your internetwork. The easiest way to stop RIP updates from propagating out an interface is to use the passive-interface global configuration command.
How do you display the contents of a Cisco IP routing table?
The show ip route command displays the Cisco routing table's contents.
What is Interior Gateway Routing Protocol (IGRP)?
IGRP is a Cisco proprietary distance vector routing protocol. IGRP has a default hop count of 100 hops, with a maximum hop count of 255. IGRP uses bandwidth and line delay as its default metric, but it can also use reliability, load, and MTU.
How do you enable IGRP on a Cisco router?
The way you enable IGRP on a Cisco router is similar to the way you enable RIP, except you specify IGRP as the protocol and add an autonomous system number. For example:
RouterA(config)#router igrp 10 (10 is the AS number)
RouterA(config-router)#network 192.168.0.0
RouterA(config-router)#network 192.168.1.0
RouterA(config-router)#network 192.168.2.0
What four timers does IGRP use to regulate its performance?
The four timers IGRP uses to regulate its performance are as follows:
• Route update timer Time between router updates The default is 90 seconds.
• Route invalid timer Time that must expire before a route becomes invalid . The default is 270 seconds.
• Route hold-down timer If a destination becomes unreachable, or if the next-hop router increases the metric recording in the routing table, the router goes into holddown for 280 seconds.
• Route flush timer[md]Time from when a route becomes invalid to when it is removed from the routing table. The default is 630 seconds.
Quick Notes - SWITCHING
What are three types of LAN traffic?
Unicasts - intended for one host.
Broadcasts - intended for everyone.
Multicasts - intended for a only a subset or group within an entire network.
What are unicast frames?
Unicast frames are the most common type of network traffic. A unicast frame is a frame intended for only one host. The only station that processes this frame is one station that has its own MAC address in the destination portion of packet.
What are broadcast frames?
Broadcast frames are frames intended for everyone. Stations view broadcast frames as public service announcements. All stations receive and process broadcast frames. In large networks, broadcasts can cause serious performance degradation in network hosts - (broadcast storm).
The destination address of broadcast frames (Data Link / Layer 2 broadcast addresses is FF-FF-FF-FF-FF-FF or alternatively all 1s in binary (11111111).
What are multicast frames?
Multicast frames address a group of devices that have a common interest. These frames allow the source to send only one copy of the frame on the network even though it is intended for several stations. Only stations that have a card that is configured by software to receive multicast frames for a particular multicast group can process a frame to that multicast address - all other stations discard multicast frames
What three major functions do Data Link Layer / Layer 2 Switches perform?
Address learning
Packet forwarding/filtering
Loop avoidance by spanning tree
What will occur when you attempt to segment a network with hubs and repeaters?
Basically, hubs and repeaters become extensions of the physical cable plant. All devices that connect to either a hub or a repeater share the same bandwidth and by definition hubs and repeaters create a single broadcast and collision domain.
Think of both devices are pass-through devices much like a electrical power-strip. Hubs and repeaters reside on the Physical Layer / Layer 1 of the OSI model where they pass 0s and 1s along the wire or up to the Data Link Layer. CSUs / Channel Service Units fall into the same category. All are regarded as unintelligent devices. No addressing takes place on the Physical layer.
What three devices are used to segment a LAN?
Router - logical addressing - IP address
Switch - physical addressing - MAC address
Bridge - physical addressing - MAC addres
What is microsegmentation?
Each workstation or network device on the network has its own dedicated segment - also known as a Collision Domain - to a switch. Each device gets the segments full bandwidth and does not have to share the dedicated segment with other devices. Collisions are reduced because each segment is its own Collision Domain.
Important: Full-duplex transmission is achieved by microsegmentation. Each device can send and receive at the same time which doubles the amount of bandwidth between nodes.
What are the three switching methods in Cisco Catalyst switches?
The three frame operating modes to handle frame switching are
Store-and-forward
Cut-through
Fragment-free
What is the Cisco Catalyst store-and-forward switching method?
In the store-and-forward switching method, the switch receives the entire frame before it forwards it. The switch reads the cyclic redundancy check (CRC) to make sure the frame is not bad. If the frame is good, the switch forwards it. Because the switch stores the frame before forwarding it, latency is introduced in the switch. Latency through the switch varies with the size of the frame.
What is the Cisco Catalyst cut-through switching method?
In cut-through switching mode, the switch only checks the frame's destination address and immediately begins forwarding the frame out the appropriate port. Because the switch checks the destination address in only the header and not the entire frame, the switch forwards a collision frame or a frame that has a bad CRC.
What is the Cisco Catalyst fragment-free switching method?
Also known as modified cut-through, fragment-free switching checks the first 64 bytes before forwarding the frame. Ethernet specifications state that collisions should be detected during the first 64 bytes of the frame. By reading the first 64 bytes of the frame, the switch can filter most collisions, although late collisions are still possible.
What is the default switching mode in Cisco Catalyst 1900 switches?
The default switching mode for the Catalyst 1900 is fragment-free.
What is half-duplex transmission mode?
Half-duplex transmission is the default mode that Ethernet functions in. In half-duplex transmission, a device can only send or receive--not do both at once. In half-duplex mode, stations are susceptible to collisions, and efficiency is rated at 50 to 60 percent.
What is full-duplex transmission mode?
In full-duplex mode, a station can send and receive at the same time. In full-duplex mode, collision detection is disabled. This mode offers 100 percent efficiency in both directions.
On a Cisco Catalyst 1900 switch, what are the default duplex settings for 10BaseT/100BaseT ports, default switching mode, and default protocols?
What are dynamic addresses on a Catalyst switch?
Dynamic addresses are addresses that the switch learns about dynamically through the learning process. If the switch does not see a MAC address for a certain amount of time, it drops the MAC address.
What are permanent MAC addresses on a Catalyst switch?
Permanent MAC addresses are entered manually by the administrator and are not aged out.
Quick Notes - Network Management
What is the Cisco Discovery Protocol (CDP)?
CDP is a Cisco proprietary protocol that runs on all Cisco IOS-enabled d
Tuesday, September 30, 2008
Trainsignal Exchange server 2007
Build your own email infrastructure
* Learn Exchange Server 2007 by watching it Configured on a Live Network
* Get certified! Exam Coverage for MCTS 70-236: Microsoft Exchange Server 2007, Configuration
* Become a pro at Installing, Configuring, and Managing Exchange Server 2007
* Learn at your own pace and at a fraction of the price compared to classroom learning!
* Taught by a Microsoft MVP with an MCSE and over 10 years of real world experience
* Discover how to Develop Secure, Efficient Systems and how to Integrate OWA
* Learn how to Backup and Restore your Exchange Server 2007
* Master all the new features that come with Exchange Server 2007
* The Most Effective Way to Learn Exchange Server 2007...See Why!
* Prepare for MCSE Certification MCSE Training Information
CD1
CODE
http://rapidshare.com/files/116761123/Party2.part1.rar
http://rapidshare.com/files/116761122/Party2.part2.rar
http://rapidshare.com/files/116761520/Party2.part3.rar
http://rapidshare.com/files/116761420/Party2.part4.rar
Pass: Grab&Go
CD2
CODE
http://rapidshare.com/files/116991984/Party2-2.part1.rar
http://rapidshare.com/files/116991996/Party2-2.part2.rar
http://rapidshare.com/files/116992029/Party2-2.part3.rar
http://rapidshare.com/files/116991689/Party2-2.part4.rar
Pass: Grab&Go
* Learn Exchange Server 2007 by watching it Configured on a Live Network
* Get certified! Exam Coverage for MCTS 70-236: Microsoft Exchange Server 2007, Configuration
* Become a pro at Installing, Configuring, and Managing Exchange Server 2007
* Learn at your own pace and at a fraction of the price compared to classroom learning!
* Taught by a Microsoft MVP with an MCSE and over 10 years of real world experience
* Discover how to Develop Secure, Efficient Systems and how to Integrate OWA
* Learn how to Backup and Restore your Exchange Server 2007
* Master all the new features that come with Exchange Server 2007
* The Most Effective Way to Learn Exchange Server 2007...See Why!
* Prepare for MCSE Certification MCSE Training Information
CD1
CODE
http://rapidshare.com/files/116761123/Party2.part1.rar
http://rapidshare.com/files/116761122/Party2.part2.rar
http://rapidshare.com/files/116761520/Party2.part3.rar
http://rapidshare.com/files/116761420/Party2.part4.rar
Pass: Grab&Go
CD2
CODE
http://rapidshare.com/files/116991984/Party2-2.part1.rar
http://rapidshare.com/files/116991996/Party2-2.part2.rar
http://rapidshare.com/files/116992029/Party2-2.part3.rar
http://rapidshare.com/files/116991689/Party2-2.part4.rar
Pass: Grab&Go
Monday, June 23, 2008
My CCNP CBT collection
HelloI am preparing for my CCNP (BCMSN for now), and Iwant to share my materials with you.I will continue to update this topic with every time i will find interesting materials that will help me .......I personally prefer TraninSignal materials but Nuggets are also very helpful.Also Cisco Mentor it may be a good resource.
BCMSN
Trainsignal
http://rapidshare.com/files/83223748/trainsBCMSN.part3.rar
http://rapidshare.com/files/83221283/trainsBCMSN.part2.rar
http://rapidshare.com/files/83218384/trainsBCMSN.part1.rar
CBTNuggets
http://rapidshare.com/files/83213844/nuggetsBCMSN.part1.rar
http://rapidshare.com/files/83215417/nuggetsBCMSN.part2.rar
Student Guide
http://rapidshare.com/files/82408808/Stude...e-BCMSN-3.0.zip
Pass4Sure v2.83
http://rapidshare.com/files/82404066/812-2.83.ZIP
BSCITrainsignal
http://rapidshare.com/files/83246036/trainsBSCI.part1.rar
http://rapidshare.com/files/83249456/trainsBSCI.part2.rar
http://rapidshare.com/files/83252671/trainsBSCI.part3.rar
http://rapidshare.com/files/83255195/trainsBSCI.part4.rar
CBTNuggets
http://rapidshare.com/files/83238250/nuggetsBSCI.part1.rar
http://rapidshare.com/files/83241442/nuggetsBSCI.part2.rar
http://rapidshare.com/files/83242540/nuggetsBSCI.part3.rar
Student Guide
http://rapidshare.com/files/82408883/Stude...de-BSCI-3.0.zip
Pass4Sure v2.83
http://rapidshare.com/files/82404095/901-2.83.ZIP
ONTTrainsignal
http://rapidshare.com/files/83232804/trainsONT.part1.rar
http://rapidshare.com/files/83234952/trainsONT.part2.rar
CBTNuggets
http://rapidshare.com/files/83227195/nuggetsONT.part1.rar
http://rapidshare.com/files/83229671/nuggetsONT.part2.rar
Student Guide
http://rapidshare.com/files/82409049/Stude...ide-ONT-1.0.zip
Pass4Sure v2.83
http://rapidshare.com/files/82404146/845-2.83.ZIP
ISCWTrainsignal.. not released yet
CBTNuggets
http://rapidshare.com/files/83258476/nuggetsISCW.part1.rar
http://rapidshare.com/files/83259873/nuggetsISCW.part2.rar
Student Guide
http://rapidshare.com/files/82408966/Stude...de-ISCW-1.0.zip
Pass4Sure v2.93
http://rapidshare.com/files/82404133/825-2.93.ZIP
CCNP Video Mentor fromCisco
http://rapidshare.com/files/83284222/CCNPvideoMentor.part08.rar
http://rapidshare.com/files/83281474/CCNPvideoMentor.part07.rar
http://rapidshare.com/files/83278350/CCNPvideoMentor.part06.rar
http://rapidshare.com/files/83275109/CCNPvideoMentor.part05.rar http://rapidshare.com/files/83271985/CCNPvideoMentor.part04.rar
http://rapidshare.com/files/83268931/CCNPvideoMentor.part03.rar
http://rapidshare.com/files/83265903/CCNPvideoMentor.part02.rar
http://rapidshare.com/files/83262873/CCNPvideoMentor.part01.rar
Bosom netsim 7
http://rapidshare.com/files/82433291/Netsim_7.0_CCNP.7z
BCMSN
Trainsignal
http://rapidshare.com/files/83223748/trainsBCMSN.part3.rar
http://rapidshare.com/files/83221283/trainsBCMSN.part2.rar
http://rapidshare.com/files/83218384/trainsBCMSN.part1.rar
CBTNuggets
http://rapidshare.com/files/83213844/nuggetsBCMSN.part1.rar
http://rapidshare.com/files/83215417/nuggetsBCMSN.part2.rar
Student Guide
http://rapidshare.com/files/82408808/Stude...e-BCMSN-3.0.zip
Pass4Sure v2.83
http://rapidshare.com/files/82404066/812-2.83.ZIP
BSCITrainsignal
http://rapidshare.com/files/83246036/trainsBSCI.part1.rar
http://rapidshare.com/files/83249456/trainsBSCI.part2.rar
http://rapidshare.com/files/83252671/trainsBSCI.part3.rar
http://rapidshare.com/files/83255195/trainsBSCI.part4.rar
CBTNuggets
http://rapidshare.com/files/83238250/nuggetsBSCI.part1.rar
http://rapidshare.com/files/83241442/nuggetsBSCI.part2.rar
http://rapidshare.com/files/83242540/nuggetsBSCI.part3.rar
Student Guide
http://rapidshare.com/files/82408883/Stude...de-BSCI-3.0.zip
Pass4Sure v2.83
http://rapidshare.com/files/82404095/901-2.83.ZIP
ONTTrainsignal
http://rapidshare.com/files/83232804/trainsONT.part1.rar
http://rapidshare.com/files/83234952/trainsONT.part2.rar
CBTNuggets
http://rapidshare.com/files/83227195/nuggetsONT.part1.rar
http://rapidshare.com/files/83229671/nuggetsONT.part2.rar
Student Guide
http://rapidshare.com/files/82409049/Stude...ide-ONT-1.0.zip
Pass4Sure v2.83
http://rapidshare.com/files/82404146/845-2.83.ZIP
ISCWTrainsignal.. not released yet
CBTNuggets
http://rapidshare.com/files/83258476/nuggetsISCW.part1.rar
http://rapidshare.com/files/83259873/nuggetsISCW.part2.rar
Student Guide
http://rapidshare.com/files/82408966/Stude...de-ISCW-1.0.zip
Pass4Sure v2.93
http://rapidshare.com/files/82404133/825-2.93.ZIP
CCNP Video Mentor fromCisco
http://rapidshare.com/files/83284222/CCNPvideoMentor.part08.rar
http://rapidshare.com/files/83281474/CCNPvideoMentor.part07.rar
http://rapidshare.com/files/83278350/CCNPvideoMentor.part06.rar
http://rapidshare.com/files/83275109/CCNPvideoMentor.part05.rar http://rapidshare.com/files/83271985/CCNPvideoMentor.part04.rar
http://rapidshare.com/files/83268931/CCNPvideoMentor.part03.rar
http://rapidshare.com/files/83265903/CCNPvideoMentor.part02.rar
http://rapidshare.com/files/83262873/CCNPvideoMentor.part01.rar
Bosom netsim 7
http://rapidshare.com/files/82433291/Netsim_7.0_CCNP.7z
Friday, June 20, 2008
IT Success
I know that nearly Everyone wanted to get success in their life. To get certified and hopefully either get a job or be promoted. In anyway, unless you are not ever going to be tested in the real world, it makes no sense to just cram these dumps and pass your exams.
My advice: Get some experience of actually using/doing things with your field of technology. If you are studying MS exams, get training videos from Train Signal or CBT and create virtual labs. It is so much better for your career if you know how the product actually works. After all, you just pretty much are trying to figure out how a product runs. It isn't rocket science! It does not matter then, whether you use dumps and pass the proceeding exams. It's because you actually studied hands on!
IT world has a lot of perks. You can go from a low paying helpdesk role to a senior infrastructure consultant getting a 6 figure salary. However, I have noticed that communication is the key. It does not matter how many certs you have, or how good you are at break-fix work, it’s whether you can communicate with your fellow engineers and clients. I believe if you all start your careers aiming to become a manager or leader of some sort, you will sort this essential component out. You will make sure you can communicate well. You will act more professional and get recognised for it.
So here you have it. If you are an engineer or a wannabe engineer and want to better your career, do the following:
1) Study hands on - Create virtual labs, do the certs. Looks a lot better when someone who has MCSE or CCA against their name can actually back that up!
2) Learn to communicate better - Go into your daily routine at work aiming to be one day a manager or leader. You will naturally learn to communicate more professionally, behave more professionally and act more professional. You will eventually get noticed.
3) Be Ambitious! Set aims. I believe if you doing the same role for over 2/3 years then you really need to move on. If you career is not taking you anywhere, even after moving jobs or taking certs then change your career! It's never too late. Don't be afraid of moving out of your comfort zone.
Finally, living a life means keeping life interesting. Wealth is very important and should be a major focus of one's life. IT career is all good, but you can easily earn money on the side whether that is through investment in shares, real estate or business. It is so important that you have something else going on in your life besides your day job! No matter your age, go and invest in something that will reward you financially down the track. Wasting your money on cars and entertainment is not the right way.
After all, IT career usually means being someone else's bitch. You would rather live your life in a worry free world if you make the right decisions now!
My advice: Get some experience of actually using/doing things with your field of technology. If you are studying MS exams, get training videos from Train Signal or CBT and create virtual labs. It is so much better for your career if you know how the product actually works. After all, you just pretty much are trying to figure out how a product runs. It isn't rocket science! It does not matter then, whether you use dumps and pass the proceeding exams. It's because you actually studied hands on!
IT world has a lot of perks. You can go from a low paying helpdesk role to a senior infrastructure consultant getting a 6 figure salary. However, I have noticed that communication is the key. It does not matter how many certs you have, or how good you are at break-fix work, it’s whether you can communicate with your fellow engineers and clients. I believe if you all start your careers aiming to become a manager or leader of some sort, you will sort this essential component out. You will make sure you can communicate well. You will act more professional and get recognised for it.
So here you have it. If you are an engineer or a wannabe engineer and want to better your career, do the following:
1) Study hands on - Create virtual labs, do the certs. Looks a lot better when someone who has MCSE or CCA against their name can actually back that up!
2) Learn to communicate better - Go into your daily routine at work aiming to be one day a manager or leader. You will naturally learn to communicate more professionally, behave more professionally and act more professional. You will eventually get noticed.
3) Be Ambitious! Set aims. I believe if you doing the same role for over 2/3 years then you really need to move on. If you career is not taking you anywhere, even after moving jobs or taking certs then change your career! It's never too late. Don't be afraid of moving out of your comfort zone.
Finally, living a life means keeping life interesting. Wealth is very important and should be a major focus of one's life. IT career is all good, but you can easily earn money on the side whether that is through investment in shares, real estate or business. It is so important that you have something else going on in your life besides your day job! No matter your age, go and invest in something that will reward you financially down the track. Wasting your money on cars and entertainment is not the right way.
After all, IT career usually means being someone else's bitch. You would rather live your life in a worry free world if you make the right decisions now!
Monday, June 9, 2008
Server Support interview question.!
1) How to enable telnet in Windows ?
2) What are the different types of Terminal Services ?
3) What is the diff between Application mode and Administration mode ?
4) What is Licensing in Terminal Services?
5) What is FSMO roles and explain ?
6) I have a Global Catalog server in Server1, and want to make the same server as a Infrasture Master. Can i go ahead with that ? Explain.
7) How to publish a web site in IIS?
8) How to deploy a patches to the systems ?
9) What are the tools available for Patch Deployments ?
10) Difference between Differential and Incremental Backup ?
11) What is DHCP Option, Server Options?
12) How to take backup in Group Policy?
13) Which component is used for replication between the sites?
14) How to take the backup DHCP data while DHCP SERVER is running?
15) What is new features in Windows 2003 DNS?
16) What are new ADS features in 2003 ?
17) You are having high configuration server SERVER1 and additional domain controller with less configuration serv2, serv3. When the 1000 users login into their computer, all login traffic goes to serv2 and serv3. so the server serv2 and serv3 get hung. How do you redirect the logon traffic to SERVER1?
18) What is the procedure to restore the data in ADS?
19) What is the use of ntdsutil command ?
20) Which command helps to find the server for FSMO roles ?
21) What are the protocol supports for Replication ?
22) What is the expantion of .Dit ? Scalable size of NTDS in 2k3?
23) What are the partitions available in AD?
24) What are the two types of replications?
25) What is KCC ? What is the function of the KCC?
26) What are the two trust protocols 2k3 using ?
27) What are the trust relations available in 2k3?
28)What are the protocols used on replication?
29) What is the default time delay on replication?
30) What Different tables available in NTDS database?
31) Where is the FRS logs stored in and what is the database engine name?
32) What is tombstone object in AD? What is it’s life time?
33) What are the functions of GC?
34) What is Global catalog and GC server?
35) What are the domain functional levels in 2k3?
36) What is the hierarchy of applying Gpo in 2k3?
1 what is the difrences btwen 2k , 2k3 and xp?
2. WHAT IS THE FUNCTION OF DHCP?
3. HOW DHCP CONFIGURE?
4. What is the new major feature introduced in Exchange 2003, which was not included in Exchange 2000?
5. How can you recover a deleted mail box ?
6. what is the use of ESUtil.exe ?
7. What are the port Numbers for pop3, imap, smtp port, smtp over ssl, pop3 over ssl, imap over ssl ?
8. Difference between Exchance 2003 and 2007?
9. what is RPC over Http ?
10. What is required for using RPC over Https with MS Outlook ?
11. If you have deleted the user, after you recreated the same user. How you will give the access of previous mail box ?
12. What are the prequisite for installation of Exchange Server ?
13. What is the use of NNTP with exchange ?
14. If NNTP service get stoped, what features of exchange will be effected ?
15. Which protocol is used for Public Folder ?
16. How will take backup of Active Directory ?
17. What are the content of System State backup ?
18. 1.boot process in windows nt/xp/2000/2003
19. 2.how do you configure memory dump if c:,d:,e: & paging file is configured so and so way?
20. 3.backups ? which is better, why and which to use when?
21. 4.disaster recovery plan?
22. 5.DHCP lease process
23. 6.DNS zones, chronicle records what are they?
24. 7.DHCP relay agent where to place it?
25. 8.what is active directory compared to SAM?
26. 9.what is GC? how many required for A Tree?
27. 10.what is forest?
28. 11.Group policies?
29. 12.FSMO Roles?
30. When you use ping command, how do you recognise DNS/WINS is working ?
31. What is the difference between DNS/WINS ?
32. Do you require WINS in Windows 2000 ? Explain how ?
33. What is Active Directory ?
34 You have parentdomain xyzhq.com and the childdomains INxyz and UKxyz. When you apply a group policy in parent domain zHQ as a domain level, does it applies to its child domain INxyz and UKxyz ?
35. You take a backup on Monday as FULL and Tuesday, Wednesday, Thursday, Friday as Differential Backup. If your Server Crashes on Friday. Then what are the media tape required to restore the date ? Explain how ?
36. What is Global Catalog Server ?
37. Can GC Server and Infrastructure place in single server ? ifnot explain why ?
38. What is the size of log file which created before updating into ntds.dit and the total number of files ?
39. What does SYSVOL contains ?
40. Which is service in your windows is responsible for replication of Domain controller to another domain controller.
41. How data will travel between sites in ADS replication?
42. What is the port number for SMTP, Kerberos, LDAP, GC Server. ?
43. What Intrasite and Intersite Replication ?
44. What is lost & found folder in ADS ?
45. What is Garbage collection ?
46. What System State data contains ?
47. How do you restore a particular OU which deleted by accidently ?
48. What is IPSec Policy ?
49. What are different types of Group Policy ?
50. What is the order of applying Group Policy ?
51. What are the new features in Windows 2003 related to ADS, Repllication, Trust ?
52. How to edit the Schma in ADS ?
53. What is Domain Local, Global Group, Universal group ?
54. Diff between Global & Universal group ?
55. What are the different types of Terminal Services ?
56. What does mean by root DNS servers?
57. What are the different records in DNS ?
58. What is SOA records ?
59. How does the downlevel clients register it names with DNS server ?
60. What is RsOP ?
61. What is default lease period for DHCP Server?
62. What is the process of DHCP clients for getting the ip address?
63. What is multicaste ?
64. What is superscope ?
65. What is the System Startup process ?
66. What is WINS hybrid & mixed mode?
67. What is Disk Quota ?
68 .What is Active Directory?
69. What is LDAP?
70. Can you connect Active Directory to other 3rd-party Directory Services? Name a few options.
71. Where is the AD database held? What other folders are related to AD?
72. What is the SYSVOL folder?
73. Name the AD NCs and replication issues for each NC
74. What are application partitions? When do I use them
75. How do you create a new application partition
76. How do you view replication properties for AD partitions and DCs?
77. What is the Global Catalog?
78. How do you view all the GCs in the forest?
79. Why not make all DCs in a large forest as GCs?
80. Trying to look at the Schema, how can I do that?
81. What are the Support Tools? Why do I need them?
82. What is LDP? What is REPLMON? What is ADSIEDIT? What is NETDOM? What is REPADMIN?
What are sites? What are they used for?
83. What's the difference between a site link's schedule and interval?
84. What is the KCC?
85. What is the ISTG? Who has that role by default?
86. What are the requirements for installing AD on a new server?
87. What can you do to promote a server to DC if you're in a remote location with slow WAN link?
How can you forcibly remove AD from a server, and what do you do later? • Can I get user passwords from the AD database?
88. What tool would I use to try to grab security related packets from the wire?
Name some OU design considerations.
89. What is tombstone lifetime attribute?
90. What do you do to install a new Windows 2003 DC in a Windows 2000 AD?
91. What do you do to install a new Windows 2003 R2 DC in a Windows 2003 AD?
92. How would you find all users that have not logged on since last month?
What are the DS* commands?
93. What's the difference between LDIFDE and CSVDE? Usage considerations?
94. What are the FSMO roles? Who has them by default? What happens when each one fails?
95. What FSMO placement considerations do you know of?
96. I want to look at the RID allocation table for a DC. What do I do?
97. What's the difference between transferring a FSMO role and seizing one? Which one should you NOT seize? Why?
98. How do you configure a "stand-by operation master" for any of the roles?
99. How do you backup AD?
100. How do you restore AD?
101. How do you change the DS Restore admin password?
102. Why can't you restore a DC that was backed up 4 months ago?
103. What are GPOs?
104. What is the order in which GPOs are applied?
105 Name a few benefits of using GPMC.
106. What are the GPC and the GPT? Where can I find them?
107. What are GPO links? What special things can I do to them?
108. What can I do to prevent inheritance from above?
109. How can you determine what GPO was and was not applied for a user? Name a few ways to do that.
110. A user claims he did not receive a GPO, yet his user and computer accounts are in the right OU, and everyone else there gets the GPO. What will you look for?
111. Name some GPO settings in the computer and user parts.
112. What are administrative templates?
113. What's the difference between software publishing and assigning?
114. Can I deploy non-MSI software with GPO?
115.You want to standardize the desktop environments (wallpaper, My Documents, Start menu, printers etc.) on the computers in one department. How would you do that?
2) What are the different types of Terminal Services ?
3) What is the diff between Application mode and Administration mode ?
4) What is Licensing in Terminal Services?
5) What is FSMO roles and explain ?
6) I have a Global Catalog server in Server1, and want to make the same server as a Infrasture Master. Can i go ahead with that ? Explain.
7) How to publish a web site in IIS?
8) How to deploy a patches to the systems ?
9) What are the tools available for Patch Deployments ?
10) Difference between Differential and Incremental Backup ?
11) What is DHCP Option, Server Options?
12) How to take backup in Group Policy?
13) Which component is used for replication between the sites?
14) How to take the backup DHCP data while DHCP SERVER is running?
15) What is new features in Windows 2003 DNS?
16) What are new ADS features in 2003 ?
17) You are having high configuration server SERVER1 and additional domain controller with less configuration serv2, serv3. When the 1000 users login into their computer, all login traffic goes to serv2 and serv3. so the server serv2 and serv3 get hung. How do you redirect the logon traffic to SERVER1?
18) What is the procedure to restore the data in ADS?
19) What is the use of ntdsutil command ?
20) Which command helps to find the server for FSMO roles ?
21) What are the protocol supports for Replication ?
22) What is the expantion of .Dit ? Scalable size of NTDS in 2k3?
23) What are the partitions available in AD?
24) What are the two types of replications?
25) What is KCC ? What is the function of the KCC?
26) What are the two trust protocols 2k3 using ?
27) What are the trust relations available in 2k3?
28)What are the protocols used on replication?
29) What is the default time delay on replication?
30) What Different tables available in NTDS database?
31) Where is the FRS logs stored in and what is the database engine name?
32) What is tombstone object in AD? What is it’s life time?
33) What are the functions of GC?
34) What is Global catalog and GC server?
35) What are the domain functional levels in 2k3?
36) What is the hierarchy of applying Gpo in 2k3?
1 what is the difrences btwen 2k , 2k3 and xp?
2. WHAT IS THE FUNCTION OF DHCP?
3. HOW DHCP CONFIGURE?
4. What is the new major feature introduced in Exchange 2003, which was not included in Exchange 2000?
5. How can you recover a deleted mail box ?
6. what is the use of ESUtil.exe ?
7. What are the port Numbers for pop3, imap, smtp port, smtp over ssl, pop3 over ssl, imap over ssl ?
8. Difference between Exchance 2003 and 2007?
9. what is RPC over Http ?
10. What is required for using RPC over Https with MS Outlook ?
11. If you have deleted the user, after you recreated the same user. How you will give the access of previous mail box ?
12. What are the prequisite for installation of Exchange Server ?
13. What is the use of NNTP with exchange ?
14. If NNTP service get stoped, what features of exchange will be effected ?
15. Which protocol is used for Public Folder ?
16. How will take backup of Active Directory ?
17. What are the content of System State backup ?
18. 1.boot process in windows nt/xp/2000/2003
19. 2.how do you configure memory dump if c:,d:,e: & paging file is configured so and so way?
20. 3.backups ? which is better, why and which to use when?
21. 4.disaster recovery plan?
22. 5.DHCP lease process
23. 6.DNS zones, chronicle records what are they?
24. 7.DHCP relay agent where to place it?
25. 8.what is active directory compared to SAM?
26. 9.what is GC? how many required for A Tree?
27. 10.what is forest?
28. 11.Group policies?
29. 12.FSMO Roles?
30. When you use ping command, how do you recognise DNS/WINS is working ?
31. What is the difference between DNS/WINS ?
32. Do you require WINS in Windows 2000 ? Explain how ?
33. What is Active Directory ?
34 You have parentdomain xyzhq.com and the childdomains INxyz and UKxyz. When you apply a group policy in parent domain zHQ as a domain level, does it applies to its child domain INxyz and UKxyz ?
35. You take a backup on Monday as FULL and Tuesday, Wednesday, Thursday, Friday as Differential Backup. If your Server Crashes on Friday. Then what are the media tape required to restore the date ? Explain how ?
36. What is Global Catalog Server ?
37. Can GC Server and Infrastructure place in single server ? ifnot explain why ?
38. What is the size of log file which created before updating into ntds.dit and the total number of files ?
39. What does SYSVOL contains ?
40. Which is service in your windows is responsible for replication of Domain controller to another domain controller.
41. How data will travel between sites in ADS replication?
42. What is the port number for SMTP, Kerberos, LDAP, GC Server. ?
43. What Intrasite and Intersite Replication ?
44. What is lost & found folder in ADS ?
45. What is Garbage collection ?
46. What System State data contains ?
47. How do you restore a particular OU which deleted by accidently ?
48. What is IPSec Policy ?
49. What are different types of Group Policy ?
50. What is the order of applying Group Policy ?
51. What are the new features in Windows 2003 related to ADS, Repllication, Trust ?
52. How to edit the Schma in ADS ?
53. What is Domain Local, Global Group, Universal group ?
54. Diff between Global & Universal group ?
55. What are the different types of Terminal Services ?
56. What does mean by root DNS servers?
57. What are the different records in DNS ?
58. What is SOA records ?
59. How does the downlevel clients register it names with DNS server ?
60. What is RsOP ?
61. What is default lease period for DHCP Server?
62. What is the process of DHCP clients for getting the ip address?
63. What is multicaste ?
64. What is superscope ?
65. What is the System Startup process ?
66. What is WINS hybrid & mixed mode?
67. What is Disk Quota ?
68 .What is Active Directory?
69. What is LDAP?
70. Can you connect Active Directory to other 3rd-party Directory Services? Name a few options.
71. Where is the AD database held? What other folders are related to AD?
72. What is the SYSVOL folder?
73. Name the AD NCs and replication issues for each NC
74. What are application partitions? When do I use them
75. How do you create a new application partition
76. How do you view replication properties for AD partitions and DCs?
77. What is the Global Catalog?
78. How do you view all the GCs in the forest?
79. Why not make all DCs in a large forest as GCs?
80. Trying to look at the Schema, how can I do that?
81. What are the Support Tools? Why do I need them?
82. What is LDP? What is REPLMON? What is ADSIEDIT? What is NETDOM? What is REPADMIN?
What are sites? What are they used for?
83. What's the difference between a site link's schedule and interval?
84. What is the KCC?
85. What is the ISTG? Who has that role by default?
86. What are the requirements for installing AD on a new server?
87. What can you do to promote a server to DC if you're in a remote location with slow WAN link?
How can you forcibly remove AD from a server, and what do you do later? • Can I get user passwords from the AD database?
88. What tool would I use to try to grab security related packets from the wire?
Name some OU design considerations.
89. What is tombstone lifetime attribute?
90. What do you do to install a new Windows 2003 DC in a Windows 2000 AD?
91. What do you do to install a new Windows 2003 R2 DC in a Windows 2003 AD?
92. How would you find all users that have not logged on since last month?
What are the DS* commands?
93. What's the difference between LDIFDE and CSVDE? Usage considerations?
94. What are the FSMO roles? Who has them by default? What happens when each one fails?
95. What FSMO placement considerations do you know of?
96. I want to look at the RID allocation table for a DC. What do I do?
97. What's the difference between transferring a FSMO role and seizing one? Which one should you NOT seize? Why?
98. How do you configure a "stand-by operation master" for any of the roles?
99. How do you backup AD?
100. How do you restore AD?
101. How do you change the DS Restore admin password?
102. Why can't you restore a DC that was backed up 4 months ago?
103. What are GPOs?
104. What is the order in which GPOs are applied?
105 Name a few benefits of using GPMC.
106. What are the GPC and the GPT? Where can I find them?
107. What are GPO links? What special things can I do to them?
108. What can I do to prevent inheritance from above?
109. How can you determine what GPO was and was not applied for a user? Name a few ways to do that.
110. A user claims he did not receive a GPO, yet his user and computer accounts are in the right OU, and everyone else there gets the GPO. What will you look for?
111. Name some GPO settings in the computer and user parts.
112. What are administrative templates?
113. What's the difference between software publishing and assigning?
114. Can I deploy non-MSI software with GPO?
115.You want to standardize the desktop environments (wallpaper, My Documents, Start menu, printers etc.) on the computers in one department. How would you do that?
MCSE FAQ
FSMO ROLES
1) While Active Directory is a distributed system, some servers only carry out specific roles. If something happens to this server or you need a more substantial server to handle a particular role, you must know which servers are handling each role.
There are five FSMO roles:
• PDC emulator (one per domain): This role allows Windows Server 2003 to act as a Windows NT primary domain controller (PDC), and it provides replication support for Windows NT-based backup domain controllers (BDCs). In addition, this role assists with time and group policy synchronization.
• Infrastructure master (one per domain): This role is responsible for updating the group-to-user references whenever the members of groups change or receive new names.
• Relative ID (RID) master (one per domain): This role ensures that every object created has a unique identification number.
• Schema master (one per forest): This role is responsible for maintaining and modifying the Active Directory schema.
• Domain naming master (one per forest): This role is responsible for the addition and deletion of domains in a forest.
How can you determine which servers hold these roles in an Active Directory forest? To find the PDC emulator, the infrastructure master, and the RID master, follows these steps:
1. Go to Start | Administrative Tools | Active Directory Users and Computers.
2. Right-click the domain and select Operations Master.
The resulting three tabs will show you which server holds each respective role.
To find the schema master, follow these steps:
1. Go to Start | Run.
2. Enter regsvr32 schmmgmt.dll in the Open text box, and click OK.
3. Go to Start | Run.
4. Enter mmc in the Open text box, and click OK.
5. Go to File | Add/Remove Snap-In, and click Add.
6. Click Active Directory Schema, click Add, click Close, and click OK.
7. Right-click Active Directory Schema and select Operations Master from the shortcut menu.
To find the domain naming master, follow these steps:
1. Go to Start | Administrative Tools | Active Directory Domains and Trusts.
2. Right-click Active Directory Domains and Trusts, and select Operations Master from the list.
Transferring the RID Master, PDC Emulator, and Infrastructure Masters via GUI
To Transfer the Domain-Specific RID Master, PDC Emulator, and Infrastructure Master FSMO Roles:
1. Open the Active Directory Users and Computers snap-in from the Administrative Tools folder.
2. If you are NOT logged onto the target domain controller, in the snap-in, right-click the icon next to Active Directory Users and Computers and press Connect to Domain Controller.
3. Select the domain controller that will be the new role holder, the target, and press OK.
4. Right-click the Active Directory Users and Computers icon again and press Operation Masters.
5. Select the appropriate tab for the role you wish to transfer and press the Change button.
6. Press OK to confirm the change.
7. Press OK all the way out.
DHCP LEASE PROCESS
1. Discover: The host will initially send a broadcast in an attempt to discover a DHCP server on the network.
2. Offer: The DHCP server will 'see' the workstation looking for the DHCP service and respond with an 'offer', which is an IP address.
3. Request: The client will receive the 'offer' and, in most cases, will accept it. This means it sends an 'official request' for the same IP address offered previously by the server.
4. Accept: The DHCP server will complete the transaction by sending an 'accept' message and marking the particular IP address for the specific host.
DHCP SERVER- Dynamic host configuration protocol is used to automatically assign TCP/IP addresses to clients along with the correct subnet mask, default gateway, and DNS server.
169.254.0.0 -169.254.255.255-APIPA Address
BOOTP- short for Bootstrap Protocol is a UDP network protocol used by a network client to obtain its IP address automatically. This is usually done during the bootstrap process when a computer is starting up. The BOOTP servers assign the IP address from a pool of addresses to each client.
BOOTP/DHCP differences
There are significant differences in the way in which BOOTP and DHCP perform host configuration. The following table compares and contrasts the features of the two protocols that vary.
BOOTP DHCP
Designed prior to DHCP. Designed after BOOTP.
Intended to configure diskless workstations with limited boot capabilities. Intended to configure frequently relocated networked computers (such as portables) that have local hard drives and full boot capabilities.
Dynamic BOOTP has default 30-day expiration on IP address leases. DHCP has default eight-day expiration on IP address leases.
Supports a limited number of client configuration parameters called vendor extensions. Supports a larger and extensible set of client configuration parameters called options.
Describes a two-phase bootstrap configuration process, as follows:
• Clients contact BOOTP servers to perform address determination and boot file name selection.
• Clients contact Trivial File Transfer Protocol (TFTP) servers to perform file transfer of their boot image.
Describes a single-phase boot configuration process whereby a DHCP client negotiates with a DHCP server to determine its IP address and obtain any other initial configuration details it needs for network operation.
BOOTP clients do not rebind or renew configuration with the BOOTP server except when the system restarts. DHCP clients do not require a system restart to rebind or renew configuration with the DHCP server. Instead, clients automatically enter a rebinding state at set timed intervals to renew their leased address allocation with the DHCP server. This process occurs in the background and is transparent to the user.
ARP (Address Resolution Protocol)
Address Resolution Protocol (ARP) is a protocol for mapping an Internet Protocol address (IP address) to a physical machine address.
RARP (Reverse Address Resolution Protocol)
Address Resolution Protocol (ARP) is a protocol for mapping a physical machine address to Internet Protocol address (IP address).
DHCP Relay Agent
The DHCP Relay Agent component is a Bootstrap Protocol (BOOTP) relay agent that relays Dynamic Host Configuration Protocol (DHCP) messages between DHCP clients and DHCP servers on different IP networks. The DHCP Relay Agent is compliant with RFC 1542. You cannot use the DHCP Relay Agent component on a computer running the DHCP service. BOOTP is a host configuration protocol developed before DHCP that was designed to configure diskless workstations with limited boot capabilities
RAID types
RAID-0: RAID-0 is called disk "striping". All the data is spread out in chunks across all the disks in the RAID set. RAID-0 has great performance, because you spread out the load of storing data onto more physical drives. There is no parity generated for RAID-0. Therefore there is no overhead to write data to RAID-0 disks. RAID-0 is only good for better performance, and not for high availability, since parity is not generated for RAID-0 disks. RAID-0 requires at least two physical disks.
RAID-1: RAID-1 is called disk mirroring. All the data is written to at least two separate physical disks. The disks are essentially mirror images of each other. If one of the disks fails, the other can be used to retrieve data. Disk mirroring is good for very fast read operations. It's slower when writing to the disks, since the data needs to be written twice. RAID-1 requires at least two physical disks.
RAID-5: RAID-5 uses disk striping with parity. The data is striped across all the disks in the RAID set, along with the parity information needed to reconstruct the data in case of disk failure. RAID-5 is the most common method used, since it achieves a good balance between performance and availability. RAID-5 requires at least three physical disks.
How do I Backup Active Directory?
Backing up Active Directory is essential to maintain an Active Directory database. You can back up Active Directory by using the Graphical User Interface (GUI) and command-line tools that the Windows Server 2003 family provides.
You frequently backup the system state data on domain controllers so that you can restore the most current data. By establishing a regular backup schedule, you have a better chance of recovering data when necessary.
To ensure a good backup includes at least the system state data and contents of the system disk, you must be aware of the tombstone lifetime. By default, the tombstone is 60 days. Any backup older than 60 days is not a good backup. Plan to backup at least two domain controllers in each domain, one of at least one backup to enable an authoritative restore of the data when necessary.
System State Data
Several features in the windows server 2003 family make it easy to backup Active Directory. You can backup Active Directory while the server is online and other network function can continue to function.
System state data on a domain controller includes the following components:
• Active Directory system state data does not contain Active Directory unless the server, on which you are backing up the system state data, is a domain controller. Active Directory is present only on domain controllers.
• The SYSVOL shared folder: This shared folder contains Group policy templates and logon scripts. The SYSVOL shared folder is present only on domain controllers.
• The Registry: This database repository contains information about the computer's configuration.
• System startup files: Windows Server 2003 requires these files during its initial startup phase. They include the boot and system files that are under windows file protection and used by windows to load, configure, and run the operating system.
• The COM+ Class Registration database: The Class registration is a database of information
about Component Services applications.
• The Certificate Services database: This database contains certificates that a server running Windows server 2003 uses to authenticate users. The Certificate Services database is present only if the server is operating as a certificate server.
System state data contains most elements of a system's configuration, but it may not include all of the information that you require recovering data from a system failure. Therefore, be sure to backup all boot and system volumes, including the System State, when you back up your server.
BOOT PROCESS-XP, 2000, 2003
First is the POST, this stands for Power on Self Test, for the computer. This process tests memory as well as a number of other subsystems. You can usually monitor this as it runs each test. After that is complete the system will run POST for any device that has BIOS (Basic Input-Output System). An AGP has its own BIOS, as do some network cards and various other devices.
Once the POST is complete and the BIOS is sure that everything is working properly, the BIOS will then attempt to read the MBR (Master Boot Record). This is the first sector of the first hard drive (called the Master or HD0). When the MBR takes over it means that Windows is now in control.
The MBR looks at the BOOT SECTOR (the first sector of the active partition). That is where NTLDR is located; NTLDR is the BOOT LOADER for Windows XP. NTLDR will allow memory addressing, initiate the file system, read the boot.ini and load the boot menu. NTLDR has to be in the root of the active partition as do NTDETECT.COM, BOOT.INI, BOOTSECT.DOS (for multi-OS booting) and NTBOOTDD.SYS (if you have SCSI adapters)
Once XP is selected from the Boot Menu, NTLDR will run NTDETECT.COM, BOOT.INI and BOOTSECT.DOS to get the proper OS selected and loaded. The system starts in 16-bit real mode and then moves into 32-bit protected mode.
NTLDR will then load NTOSKRNL.EXE and HAL.DLL. Effectively, these two files are windows XP. They must be located in %SystemRoot%System32.
NTLDR reads the registry, chooses a hardware profile and authorizes device drivers, in that exact order.
At this point NTOSKRNL.EXE takes over. It starts WINLOGON.EXE that in turn starts LSASS.EXE; this is the program that displays the Logon screen so that you can logon.
Sample Boot.ini File
This is a sample of a default Boot.ini file from a Windows XP Professional computer.
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fast detect
TYPES OF WINDOWS 2003
Standard Edition-4 processors with up to 4 GB RAM
Enterprise Edition-eight processors with up to 32 GB memory.
Datacenter Edition-32 processors with up to 64 GB RAM.
Web Edition-supports a maximum of 2 processors with support for a maximum of 2GB of RAM
The Five IP Address Classes
Class A networks have a beginning octet of 1 - 126.
Class B networks have a beginning octet of 128-191.
Class C networks have a beginning octet of 192 - 223.
Class C networks have a beginning octet of 224 – 239.
Class C networks have a beginning octet of 224.0.0.0 - 255.255.255.255
What are the benefits of using DHCP?
A. DHCP provides the following benefits for administering your TCP/IP-based network:
• Reliable configuration
DHCP avoids configuration errors caused by the need to manually type in values at each computer. Also, DHCP helps prevent address conflicts caused by a previously assigned IP address being reused to configure a new computer on the network.
• Reduces configuration management
Using DHCP servers can greatly decrease time spent configuring and reconfiguring computers on your network. Servers can be configured to supply a full range of additional configuration values when assigning address leases. These values are assigned using DHCP options.
The DHCP lease renewal process helps assure that where client configurations need to be updated often (such as users with mobile or portable computers who change locations frequently), these changes can be made efficiently and automatically by clients communicating directly with DHCP servers.
What protocols and ports does DHCP traffic use?
All DHCP traffic uses the User Datagram Protocol (UDP). Messages from the DHCP client to the DHCP server use UDP source port 68 and UDP destination port 67. Messages from the DHCP server to the DHCP client use UDP source port 67 and UDP destination port 68.
Backing up the DHCP database
Maintaining a backup of the DHCP database protects you from data loss if the DHCP database is lost (for example, due to hard disk failure) or becomes corrupted. There are three backup methods supported by the DHCP Server service:
• Synchronous backups that occur automatically. The default backup interval is 60 minutes.
• Asynchronous (manual) backups, performed by using the Backup command on the DHCP console. For more information about asynchronous backups, see back up the DHCP database.
• Backups using Windows Backup (ntbackup.exe) or non-Microsoft backup software. For more information about Windows Backup, see Backup.
To move a DHCP database to another server
This topic provides details on how to move a DHCP database from one server computer (the source server) to another server computer (the destination server).
To back up the DHCP database (at the source server)
1. Open DHCP.
2. In the console tree, click the applicable DHCP server.
3. On the Action menu, click Backup.
4. In the Browse for Folder dialog box, select the folder that will contain the backup DHCP database, and then click OK.
5. Stop the DHCP server.
This prevents the server from assigning new address leases to clients after the database has been backed up.
For more information, see Start or stop a DHCP server.
6. Disable the DHCP Server service in the list of services.
This prevents the DHCP server from starting after the database has been transferred. For more information, see Enable or disable a service for a hardware profile.
7. Copy the folder that contains the backup DHCP database to the destination
Group policy- is a feature of Microsoft Windows NT family of operating systems that provides centralized management and configuration of computers and remote users in an Active Directory environment
DNS Query Process
A DNS query is the process of a computer or networking device making an inquiry to get an IP address for a DNS name such as w3.org
The client computer will send a DNS query to one of their internet service provider's DNS servers. The DNS server looks in it's DNS database to tell whether it can answer the query authoritatively. If the DNS server can answer authoritatively, the DNS server answers the query and the DNS query process is complete.
If the server cannot answer the query authoritatively it will look in its DNS cache of previous queries. If the DNS server finds a matching entry in its cache, it will answer the query with a non-authoritative answer based on the information in its cache and the DNS query process is complete.
If the ISP DNS server did not have the DNS information in its DNS database or its DNS cache the DNS query process will use recursion to complete the DNS query. The ISP DNS server will use its root hints file to find information to contact other DNS servers. The root hints file specified DNS servers that are authoritative for the DNS domain root and top level domains in the DNS system. This includes the .com, .org, .net, .gov and other domain types. If the query is for www.w3.org the ISP DNS server would contact an authorititative server for the top level "org" domain and send an iterative query to the org DNS server asking for information about the authoritative server for w3.org. The org domain DNS server responds with the the nameserver information including IP address of the nameserver for w3.org. Then the ISP DNS server sends a query to the w3.org DNS server asking for the IP address of www.w3c.org. The w3.org DNS server sends an authoritative answer back to the ISP DNS server which is cached in the ISP DNS server cache and also sent to the client computer.
If another client computer later does a request for information about www.w3.org the ISP DNS server has the information in its cache and will not neet to ask other DNS servers for additional information.
1) While Active Directory is a distributed system, some servers only carry out specific roles. If something happens to this server or you need a more substantial server to handle a particular role, you must know which servers are handling each role.
There are five FSMO roles:
• PDC emulator (one per domain): This role allows Windows Server 2003 to act as a Windows NT primary domain controller (PDC), and it provides replication support for Windows NT-based backup domain controllers (BDCs). In addition, this role assists with time and group policy synchronization.
• Infrastructure master (one per domain): This role is responsible for updating the group-to-user references whenever the members of groups change or receive new names.
• Relative ID (RID) master (one per domain): This role ensures that every object created has a unique identification number.
• Schema master (one per forest): This role is responsible for maintaining and modifying the Active Directory schema.
• Domain naming master (one per forest): This role is responsible for the addition and deletion of domains in a forest.
How can you determine which servers hold these roles in an Active Directory forest? To find the PDC emulator, the infrastructure master, and the RID master, follows these steps:
1. Go to Start | Administrative Tools | Active Directory Users and Computers.
2. Right-click the domain and select Operations Master.
The resulting three tabs will show you which server holds each respective role.
To find the schema master, follow these steps:
1. Go to Start | Run.
2. Enter regsvr32 schmmgmt.dll in the Open text box, and click OK.
3. Go to Start | Run.
4. Enter mmc in the Open text box, and click OK.
5. Go to File | Add/Remove Snap-In, and click Add.
6. Click Active Directory Schema, click Add, click Close, and click OK.
7. Right-click Active Directory Schema and select Operations Master from the shortcut menu.
To find the domain naming master, follow these steps:
1. Go to Start | Administrative Tools | Active Directory Domains and Trusts.
2. Right-click Active Directory Domains and Trusts, and select Operations Master from the list.
Transferring the RID Master, PDC Emulator, and Infrastructure Masters via GUI
To Transfer the Domain-Specific RID Master, PDC Emulator, and Infrastructure Master FSMO Roles:
1. Open the Active Directory Users and Computers snap-in from the Administrative Tools folder.
2. If you are NOT logged onto the target domain controller, in the snap-in, right-click the icon next to Active Directory Users and Computers and press Connect to Domain Controller.
3. Select the domain controller that will be the new role holder, the target, and press OK.
4. Right-click the Active Directory Users and Computers icon again and press Operation Masters.
5. Select the appropriate tab for the role you wish to transfer and press the Change button.
6. Press OK to confirm the change.
7. Press OK all the way out.
DHCP LEASE PROCESS
1. Discover: The host will initially send a broadcast in an attempt to discover a DHCP server on the network.
2. Offer: The DHCP server will 'see' the workstation looking for the DHCP service and respond with an 'offer', which is an IP address.
3. Request: The client will receive the 'offer' and, in most cases, will accept it. This means it sends an 'official request' for the same IP address offered previously by the server.
4. Accept: The DHCP server will complete the transaction by sending an 'accept' message and marking the particular IP address for the specific host.
DHCP SERVER- Dynamic host configuration protocol is used to automatically assign TCP/IP addresses to clients along with the correct subnet mask, default gateway, and DNS server.
169.254.0.0 -169.254.255.255-APIPA Address
BOOTP- short for Bootstrap Protocol is a UDP network protocol used by a network client to obtain its IP address automatically. This is usually done during the bootstrap process when a computer is starting up. The BOOTP servers assign the IP address from a pool of addresses to each client.
BOOTP/DHCP differences
There are significant differences in the way in which BOOTP and DHCP perform host configuration. The following table compares and contrasts the features of the two protocols that vary.
BOOTP DHCP
Designed prior to DHCP. Designed after BOOTP.
Intended to configure diskless workstations with limited boot capabilities. Intended to configure frequently relocated networked computers (such as portables) that have local hard drives and full boot capabilities.
Dynamic BOOTP has default 30-day expiration on IP address leases. DHCP has default eight-day expiration on IP address leases.
Supports a limited number of client configuration parameters called vendor extensions. Supports a larger and extensible set of client configuration parameters called options.
Describes a two-phase bootstrap configuration process, as follows:
• Clients contact BOOTP servers to perform address determination and boot file name selection.
• Clients contact Trivial File Transfer Protocol (TFTP) servers to perform file transfer of their boot image.
Describes a single-phase boot configuration process whereby a DHCP client negotiates with a DHCP server to determine its IP address and obtain any other initial configuration details it needs for network operation.
BOOTP clients do not rebind or renew configuration with the BOOTP server except when the system restarts. DHCP clients do not require a system restart to rebind or renew configuration with the DHCP server. Instead, clients automatically enter a rebinding state at set timed intervals to renew their leased address allocation with the DHCP server. This process occurs in the background and is transparent to the user.
ARP (Address Resolution Protocol)
Address Resolution Protocol (ARP) is a protocol for mapping an Internet Protocol address (IP address) to a physical machine address.
RARP (Reverse Address Resolution Protocol)
Address Resolution Protocol (ARP) is a protocol for mapping a physical machine address to Internet Protocol address (IP address).
DHCP Relay Agent
The DHCP Relay Agent component is a Bootstrap Protocol (BOOTP) relay agent that relays Dynamic Host Configuration Protocol (DHCP) messages between DHCP clients and DHCP servers on different IP networks. The DHCP Relay Agent is compliant with RFC 1542. You cannot use the DHCP Relay Agent component on a computer running the DHCP service. BOOTP is a host configuration protocol developed before DHCP that was designed to configure diskless workstations with limited boot capabilities
RAID types
RAID-0: RAID-0 is called disk "striping". All the data is spread out in chunks across all the disks in the RAID set. RAID-0 has great performance, because you spread out the load of storing data onto more physical drives. There is no parity generated for RAID-0. Therefore there is no overhead to write data to RAID-0 disks. RAID-0 is only good for better performance, and not for high availability, since parity is not generated for RAID-0 disks. RAID-0 requires at least two physical disks.
RAID-1: RAID-1 is called disk mirroring. All the data is written to at least two separate physical disks. The disks are essentially mirror images of each other. If one of the disks fails, the other can be used to retrieve data. Disk mirroring is good for very fast read operations. It's slower when writing to the disks, since the data needs to be written twice. RAID-1 requires at least two physical disks.
RAID-5: RAID-5 uses disk striping with parity. The data is striped across all the disks in the RAID set, along with the parity information needed to reconstruct the data in case of disk failure. RAID-5 is the most common method used, since it achieves a good balance between performance and availability. RAID-5 requires at least three physical disks.
How do I Backup Active Directory?
Backing up Active Directory is essential to maintain an Active Directory database. You can back up Active Directory by using the Graphical User Interface (GUI) and command-line tools that the Windows Server 2003 family provides.
You frequently backup the system state data on domain controllers so that you can restore the most current data. By establishing a regular backup schedule, you have a better chance of recovering data when necessary.
To ensure a good backup includes at least the system state data and contents of the system disk, you must be aware of the tombstone lifetime. By default, the tombstone is 60 days. Any backup older than 60 days is not a good backup. Plan to backup at least two domain controllers in each domain, one of at least one backup to enable an authoritative restore of the data when necessary.
System State Data
Several features in the windows server 2003 family make it easy to backup Active Directory. You can backup Active Directory while the server is online and other network function can continue to function.
System state data on a domain controller includes the following components:
• Active Directory system state data does not contain Active Directory unless the server, on which you are backing up the system state data, is a domain controller. Active Directory is present only on domain controllers.
• The SYSVOL shared folder: This shared folder contains Group policy templates and logon scripts. The SYSVOL shared folder is present only on domain controllers.
• The Registry: This database repository contains information about the computer's configuration.
• System startup files: Windows Server 2003 requires these files during its initial startup phase. They include the boot and system files that are under windows file protection and used by windows to load, configure, and run the operating system.
• The COM+ Class Registration database: The Class registration is a database of information
about Component Services applications.
• The Certificate Services database: This database contains certificates that a server running Windows server 2003 uses to authenticate users. The Certificate Services database is present only if the server is operating as a certificate server.
System state data contains most elements of a system's configuration, but it may not include all of the information that you require recovering data from a system failure. Therefore, be sure to backup all boot and system volumes, including the System State, when you back up your server.
BOOT PROCESS-XP, 2000, 2003
First is the POST, this stands for Power on Self Test, for the computer. This process tests memory as well as a number of other subsystems. You can usually monitor this as it runs each test. After that is complete the system will run POST for any device that has BIOS (Basic Input-Output System). An AGP has its own BIOS, as do some network cards and various other devices.
Once the POST is complete and the BIOS is sure that everything is working properly, the BIOS will then attempt to read the MBR (Master Boot Record). This is the first sector of the first hard drive (called the Master or HD0). When the MBR takes over it means that Windows is now in control.
The MBR looks at the BOOT SECTOR (the first sector of the active partition). That is where NTLDR is located; NTLDR is the BOOT LOADER for Windows XP. NTLDR will allow memory addressing, initiate the file system, read the boot.ini and load the boot menu. NTLDR has to be in the root of the active partition as do NTDETECT.COM, BOOT.INI, BOOTSECT.DOS (for multi-OS booting) and NTBOOTDD.SYS (if you have SCSI adapters)
Once XP is selected from the Boot Menu, NTLDR will run NTDETECT.COM, BOOT.INI and BOOTSECT.DOS to get the proper OS selected and loaded. The system starts in 16-bit real mode and then moves into 32-bit protected mode.
NTLDR will then load NTOSKRNL.EXE and HAL.DLL. Effectively, these two files are windows XP. They must be located in %SystemRoot%System32.
NTLDR reads the registry, chooses a hardware profile and authorizes device drivers, in that exact order.
At this point NTOSKRNL.EXE takes over. It starts WINLOGON.EXE that in turn starts LSASS.EXE; this is the program that displays the Logon screen so that you can logon.
Sample Boot.ini File
This is a sample of a default Boot.ini file from a Windows XP Professional computer.
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fast detect
TYPES OF WINDOWS 2003
Standard Edition-4 processors with up to 4 GB RAM
Enterprise Edition-eight processors with up to 32 GB memory.
Datacenter Edition-32 processors with up to 64 GB RAM.
Web Edition-supports a maximum of 2 processors with support for a maximum of 2GB of RAM
The Five IP Address Classes
Class A networks have a beginning octet of 1 - 126.
Class B networks have a beginning octet of 128-191.
Class C networks have a beginning octet of 192 - 223.
Class C networks have a beginning octet of 224 – 239.
Class C networks have a beginning octet of 224.0.0.0 - 255.255.255.255
What are the benefits of using DHCP?
A. DHCP provides the following benefits for administering your TCP/IP-based network:
• Reliable configuration
DHCP avoids configuration errors caused by the need to manually type in values at each computer. Also, DHCP helps prevent address conflicts caused by a previously assigned IP address being reused to configure a new computer on the network.
• Reduces configuration management
Using DHCP servers can greatly decrease time spent configuring and reconfiguring computers on your network. Servers can be configured to supply a full range of additional configuration values when assigning address leases. These values are assigned using DHCP options.
The DHCP lease renewal process helps assure that where client configurations need to be updated often (such as users with mobile or portable computers who change locations frequently), these changes can be made efficiently and automatically by clients communicating directly with DHCP servers.
What protocols and ports does DHCP traffic use?
All DHCP traffic uses the User Datagram Protocol (UDP). Messages from the DHCP client to the DHCP server use UDP source port 68 and UDP destination port 67. Messages from the DHCP server to the DHCP client use UDP source port 67 and UDP destination port 68.
Backing up the DHCP database
Maintaining a backup of the DHCP database protects you from data loss if the DHCP database is lost (for example, due to hard disk failure) or becomes corrupted. There are three backup methods supported by the DHCP Server service:
• Synchronous backups that occur automatically. The default backup interval is 60 minutes.
• Asynchronous (manual) backups, performed by using the Backup command on the DHCP console. For more information about asynchronous backups, see back up the DHCP database.
• Backups using Windows Backup (ntbackup.exe) or non-Microsoft backup software. For more information about Windows Backup, see Backup.
To move a DHCP database to another server
This topic provides details on how to move a DHCP database from one server computer (the source server) to another server computer (the destination server).
To back up the DHCP database (at the source server)
1. Open DHCP.
2. In the console tree, click the applicable DHCP server.
3. On the Action menu, click Backup.
4. In the Browse for Folder dialog box, select the folder that will contain the backup DHCP database, and then click OK.
5. Stop the DHCP server.
This prevents the server from assigning new address leases to clients after the database has been backed up.
For more information, see Start or stop a DHCP server.
6. Disable the DHCP Server service in the list of services.
This prevents the DHCP server from starting after the database has been transferred. For more information, see Enable or disable a service for a hardware profile.
7. Copy the folder that contains the backup DHCP database to the destination
Group policy- is a feature of Microsoft Windows NT family of operating systems that provides centralized management and configuration of computers and remote users in an Active Directory environment
DNS Query Process
A DNS query is the process of a computer or networking device making an inquiry to get an IP address for a DNS name such as w3.org
The client computer will send a DNS query to one of their internet service provider's DNS servers. The DNS server looks in it's DNS database to tell whether it can answer the query authoritatively. If the DNS server can answer authoritatively, the DNS server answers the query and the DNS query process is complete.
If the server cannot answer the query authoritatively it will look in its DNS cache of previous queries. If the DNS server finds a matching entry in its cache, it will answer the query with a non-authoritative answer based on the information in its cache and the DNS query process is complete.
If the ISP DNS server did not have the DNS information in its DNS database or its DNS cache the DNS query process will use recursion to complete the DNS query. The ISP DNS server will use its root hints file to find information to contact other DNS servers. The root hints file specified DNS servers that are authoritative for the DNS domain root and top level domains in the DNS system. This includes the .com, .org, .net, .gov and other domain types. If the query is for www.w3.org the ISP DNS server would contact an authorititative server for the top level "org" domain and send an iterative query to the org DNS server asking for information about the authoritative server for w3.org. The org domain DNS server responds with the the nameserver information including IP address of the nameserver for w3.org. Then the ISP DNS server sends a query to the w3.org DNS server asking for the IP address of www.w3c.org. The w3.org DNS server sends an authoritative answer back to the ISP DNS server which is cached in the ISP DNS server cache and also sent to the client computer.
If another client computer later does a request for information about www.w3.org the ISP DNS server has the information in its cache and will not neet to ask other DNS servers for additional information.
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