All in One

HappY NeW YeaR - - 2007

2006-12-30T15:44:00.000+05:30

Hi Frenz,

Wish U all Happy & Prosperous New Year - 2007

Q & A about PORT

2006-12-27T17:51:00.000+05:30

1: What is a header and why is it significant to TCP/IP?

** A header is a series of bits that is prepended to application data by TCP, UDP, and IP. These bits provide essential pieces of information that facilitate the communications between these protocol suites on the source and destination machines during a communications session.

2: What function is served by a port address?

** A port address uniquely identifies the application in a communications session. Two port addresses exist in each communications session: one to identify the source application and the other to identify the destination application.

3: What's the difference between a source port address and a destination port address?

** A source port address identifies the address of the application that initiated the conversation. A destination port address is the address of the recipient of that conversation.

4: What's the difference between a well-known, registered, and dynamic port address?

** A well-known port address can only be assigned to system-level processes. Assignment of well-known port addresses is carefully regulated by IANA, as there are only 1,024 possible addresses. These range from 0 to 1023.

A registered port address is also regulated by IANA, but these numbers can be assigned to applications run by users. Registered port numbers range from 1024 to 49151.

Dynamic port addresses are selected on the fly from a pool of available or unused port addresses. The pool of possible addresses starts at 49151 and runs up to 65535.

5: What are the four most important network-oriented functions provided by IP?

** IP performs four critical functions:

- Creating an envelope for carrying data through a network or internetwork.

- Providing a numeric addressing system that lets you uniquely identify virtually every machine in the Internet around the world.

- Enabling each envelope or data packet to be specifically addressed to its intended destination. This address is the packet's destination IP address.

- Enabling each envelope or packet of data to also tell the recipient machine who sent it. This return address is the source IP address.

6: What are the two most important network-oriented functions provided by UDP?

** UDP's two most critical functions include

- Accepting data from an application and wrapping a UDP header around it. The combined structure of UDP header and application data is known as a datagram. Unlike TCP, UDP doesn't have to segment its data. The type of applications that use UDP are such that only small quantities of data typically are passed at a time to UDP. The datagram is handed to IP for further processing.

- Verifying whether the data in the datagram was damaged in transit. If the data is found undamaged, it is handed to its intended destination application. If the data appears to have been damaged, the entire datagram is discarded.

7: What are the six most important critical network-oriented functions provided by TCP?

** TCP's top six functions include

- Chopping up application data into bite-sized chunks known as segments

- Managing the communications session

- Guaranteeing that data gets delivered to the correct destination machine and application

- Finding and fixing any damage that occurs to data when it traverses the network

- Ensuring that any data lost in transit is replaced

- Reassembling data received into a perfect copy of the application data that was sent

Cool Aish Photo's

2006-12-27T16:35:00.000+05:30

Wish U all Happy Christmas

2006-12-23T13:36:00.000+05:30

Wish U all Happy & Merry Christmas

"May Peace be your gift at Christmas and your blessing all year through!"

Basic Q & A ( switching )

2006-12-21T12:08:00.000+05:30

1. What is multilayer switching (MLS)?

** MLS forwards traffic using information from Layer 2, Layer 3, and Layer 4all in hardware at wire speed.

2.What is a collision domain, and where does it exist in a switched LAN?

** A collision domain is a network segment where shared media access is supported. Devices on the shared media must compete for access when transmitting data. In a switched network, the collision domain is restricted to a single switch port and does not extend across the switch.

3. What is a broadcast domain, and where does it exist in a switched LAN?

** A broadcast domain is the extent of a network where broadcast frames propagate. Basically, a broadcast domain covers an area where Layer 2 devices are located and terminates at the boundary of a Layer 3 device. In a switched network, the broadcast domain extends to all switch ports assigned to a common VLAN. This is because a switch forwards broadcasts out all available ports in a VLAN.

4. What is a VLAN, and why is it used?

** A virtual LAN (VLAN) is a group of switch ports that communicate as if they were attached to a single shared-media LAN segment. VLANs can extend across buildings or backbones, as long as the VLAN is connected end to end through trunking or physical connections. A VLAN is a broadcast domain. VLANs segment networks for ease of management and better performance.

5. At what OSI layers do devices in the distribution layer usually operate?

** Layers 2, 3, and 4

6. What is network segmentation? When is it necessary, and how is it done in a campus network design?

** Segmentation is the process of dividing a LAN into smaller, discrete collision domains. If a large percentage of collisions is observed on a LAN, segmentation is appropriate. In a campus network design, segmentation occurs at each switch port. A similar form of segmentation involves reducing the size of broadcast domains. Placing Layer 3 devices in the distribution and core layers terminates the broadcast domains at those layer boundaries.

Basic info about Network Standards

2006-12-20T12:27:00.000+05:30

1: What is the IETF?

** The Internet Engineering Task Force (IETF) is responsible for developing and maintaining the Internet's technologies, as well as guiding its growth and development. Consequently, the IETF is frequently regarded as the guardian of the Internet and its technologies.

2: What is the difference between open standards and closed, or proprietary, technologies?

** A closed or proprietary technology is one developed in secret. The details about how it is made or how it works are kept a secret. Conversely, an open technology is one developed publicly and whose technical details are shared freely with anyone who would like to know them.

3: What is interoperability?

** Interoperability is the ability to build a functional networked computing environment by interconnecting products from different manufacturers.

4: What is the benefit of interoperability?

** The benefit of interoperability across vendor platforms is that it makes products from different vendors compatible, thus encouraging price-based competition. The result is that it enables communications between dissimilar computer systems.

5: How do you create and maintain the technical standards that enable the Internet and its technologies to be interoperable?

** The IETF creates and maintains the technical standards that enable the Internet and its technologies to remain interoperable. It does so by sanctioning committees to study problems and develop solutions. The solutions are documented publicly in Requests For Comments (RFCs). Products that conform to the standards set forth in the RFCs interoperate regardless of who made them.

6: What is a reference model and why is it needed?

** A reference model is a logical framework that keeps a sequence of events in proper order. Reference models have been indispensable in developing open networks and systems by providing a neutral framework for all to follow.

7: Explain the concept of logical adjacency.

** Logical adjacency means that two compatible applications function as if they are passing data directly back and forth between each other. For example, you use e-mail software to send e-mails to other people using similar software. In reality, the e-mail software packages communicate indirectly. They communicate directly with TCP/IP. Simply stated, the two e-mail packages appear logically adjacent, even though they physically are not.

IP Addressing Ques (Answer urself )

2006-12-13T12:15:00.000+05:30

1. A router can determine that an IP address is part of a Class B network
by examining the first two bits in the IP address. What are the first two
bits for a Class B network?

A. 00
B. 01
C. 10
D. 11

2. What does an IP address of 127.0.0.1 indicate?

A. A local broadcast
B. A directed multicast
C. The local network
D. A local loopback

3. Which of the following subnet masks will support 50 IP addresses?

A. 255.255.255.240
B. 255.255.255.0
C. 255.255.255.192
D. 255.255.255.224

4. VLSM is compatible with which of the following routing protocols?
(Choose all that apply.)

A. RIPv1
B. RIPv2
C. IGRP
D. EIGRP

5. Which of the following best describes route summarization?

A. A router’s ability to take a group of subnetworks and summarize
them as one network advertisement
B. The Cisco IOS feature that permits serial interfaces to borrow an
IP address from another specified interface
C. The ability to tunnel IP address information inside an AURP
encapsulated frame
D. EIGRP’s ability to isolate discontiguous route advertisements from
one AS to another

6. Which of the following best summarizes the networks 172.16.100.0/24
and 172.16.106.0/24?

A. 172.16.0.0/24
B. 172.16.100.0/20
C. 172.16.106.0/20
D. 172.16.96.0/20

7. Which of the following is a good design practice for implementing
route summarization?

A. Use primarily with discontiguous networks.
B. Use primarily with contiguous networks.
C. Do not use with VLSM.
D. Use with non-hierarchical addressing.

8. Which of the following router-configuration commands would you
use to disable automatic route summarization in an EIGRP
environment?

A. no summary
B. no auto-summary
C. no summary stub
D. no route-summary

9. Which of the following are caveats of Cisco’s IP unnumbered IOS feature?
(Choose all that apply.)

A. Does not work over HDLC networks.
B. Is not compatible with SNMP.
C. Does not work over X.25 networks.
D. You cannot ping an unnumbered interface.

10. If you have a subnet mask of 255.255.255.248, what is another way
of displaying this mask?

A. /17
B. /23
C. /27
D. /29

11. Given the VLSM address 172.16.1.8/30, what are the two IP
addresses in the range that may be assigned to hosts?

A. 172.16.1.8
B. 172.16.1.9
C. 172.16.1.10
D. 172.16.1.11

12. Given an IP address of 172.16.0.10/29, what is the network address?

A. 172.16.0.8
B. 172.16.0.9
C. 172.16.0.11
D. 172.16.0.12

13. Which of the following may be done to overcome problems associated
with discontiguous networks?

A. Use route summarization.
B. Use VLSM.
C. Use IP unnumbered.
D. Disable route summarization.

14. Which of the following IP addresses do Cisco routers use to designate
the default route?

A. 1.1.1.1
B. 0.0.0.0
C. 255.255.255.255
D. 127.0.0.1

15. If you decide not to use IP unnumbered on a serial link, to best preserve
IP addresses, what should your subnet mask be?

A. 255.255.255.255
B. 255.255.255.0
C. 255.255.255.252
D. 255.255.252.0

16. What are the two methods that are most commonly used to represent
an IP address?

A. Dotted-decimal
B. Octal
C. Binary
D. Hexadecimal

Multicast in IP ( CCNP )

2006-12-06T11:35:00.000+05:30

1.By default, what does a router or Layer 3 switch do with multicast packets?

** It drops them because multicast routing is not enabled by default.

2.By default, what does a Layer 2 switch do with a multicast packet?

** It floods the packet out all ports on the source VLAN, as if it were a broadcast packet.

3.What high-order bit combination signals that an IP address is used for multicast?

** 1110

4.If the IP-to-MAC multicast address mapping is somewhat ambiguous, how can a frame be forwarded to the correct destination group?

** The IP header must be examined in addition to the multicast MAC destination address.

5.What IP multicast address range is set aside for use only on the local network segment?

** 224.0.0.0 to 224.0.0.255

6.For the RPF check, the source IP address is looked up in the unicast routing table. To forward the packet, what should the result of the test be?

** The unicast route to the source must be out the interface where the packet arrived.

7.What important difference exists between IGMPv1 and IGMPv2?

** Hosts can request to leave a multicast group immediately with IGMPv2. IGMPv1 doesn't have any mechanism for leaving a group other than an aging-out process.

8.To join a multicast group, what type of message is sent? Where is this message sent?

** An IGMP membership report is sent. The IGMP message is with a destination address of the multicast group itself so that the nearest multicast router will receive it.

9.What is the purpose of the IGMP querier?

** It is a router that periodically asks all hosts if any of them want to join the multicast group. Interested hosts must respond with a membership report.

Switching ( Multilayer Switching)

2006-12-01T19:10:00.000+05:30

1.What might you need to implement interVLAN routing?

** One or more Layer 3 interfaces
One or more SVIs
Static routes
A dynamic routing protocol

2.Can interVLAN routing be performed over a single trunk link?

** Yes. Packets can be forwarded between the VLANs carried over the trunk.

3.To configure an SVI, what commands are needed?

** First, make sure the VLAN is defined on the switch.interface vlan vlan-id
ip address ip-address mask
no shutdown

4.What command can verify the VLAN assignments on a Layer 2 port?

** show interface type mod/num switchport
orshow interface status

5.A switch has the following interface configurations in its running configuration:interface fastethernet 0/1
switchport access vlan 5
!
interface vlan 5
ip address 192.168.10.1 255.255.255.0
no shutdown
What is necessary for packets to get from the FastEthernet interface to the VLAN 5 SVI?

** Nothing. Both are assigned to VLAN 5, so normal Layer 2 transparent bridging will take care of all forwarding between the two.

6.What is the source of FIB information?

** The routing table, as computed by the Layer 3 engine portion of a switch.

7.How often is the FIB updated?

** As needed. It is downloaded or updated dynamically by the Layer 3 engine whenever the routing topology changes or an ARP entry changes.

8.What is meant by the term "CEF punt"?

** A packet can't be forwarded or switched by CEF directly because it needs further processing. The packet is "punted" to the Layer 3 engine, effectively bypassing CEF for a more involved resolution.

9.What happens to the FIB when distributed CEF (dCEF) is used?

** It is simply replicated to each of the independent CEF engines. The FIB itself remains intact so that each engine receives a duplicate copy.

10.What happens during a "CEF glean" process?

**The MAC address (ARP reply) for a next-hop FIB entry is not yet known. The Layer 3 engine must generate an ARP request and wait for a reply before CEF forwarding can continue to that destination.

11.What does a multilayer switch do to the IP TTL value just before a packet is forwarded?

** The TTL is decremented by one, as if a router had forwarded the packet.

12.What is fallback bridging?

**On switch platforms that cannot multilayer-switch (route) all routable protocols, those protocols can be bridged transparently between VLANs instead.

13.Is it possible for an SVI to go down? If so, for what reasons?

** Yes. The SVI can be shut down administratively with the shutdown command, as with any other interface. Also, if the VLAN associated with the SVI is not defined or active, the SVI will appear to be down.

Implementing BGP in Large Networks

2006-11-29T19:08:00.000+05:30

1.If a route reflector hears an update from a nonclient, what action will be taken?

** If a route reflector hears an update from a nonclient, it will reflect the update to clients only.

2: In version 11.0 of the Cisco IOS software, what method would be used to restrict routing information from being received or propagated?

** Distribute lists would be used to restrict BGP routing updates in version 11.0 of the Cisco IOS software. Prefix lists became available to ISPs in 11.2 of the IOS and in 12.0 to the general public.

3:Explain the purpose and use of the command show ip prefix-list name [seq seq-number].

** This command displays the entry prefix list with a given sequence number.

4: Why would you redistribute static routes into BGP?

** The static routes are forwarded to the nonexistent interface null 0 to aggregate the routes to create a supernet. This is then redistributed to the BGP process instead of the hundreds of routes that exist. Because any route redistributed into BGP must be in the IP routing table, this is a way of creating a supernet and having it redistributed.
A static route to null 0 is not needed if the network command is used and no address aggregation is performed, although it can be used to prevent routing loops.

5: Why is it advisable to have the route reflectors fully meshed?

** Although clients are not fully meshed within a cluster, it is important that the route reflectors they serve are fully meshed. This is to ensure that the routers pass routing information to each other. Remember that iBGP does not propagate routing information; it generates information only based on the network command. The route reflectors need to pass information to each other to ensure the entire network has a full knowledge of the network. It is possible to create a hierarchical design with route reflectors, but this should be done with great caution, as it can cause routing loops.

6: Why is filtering often required when redistributing BGP into an IGP?

** Filtering is often required when redistributing BGP into an IGP because the routing tables can become overwhelmed by the number of routes that are imported.

7: What are the advantages of multihoming?

** Multihoming allows for redundancy, which is important when the link is into the Internet and can carry crucial business information for the company. Multihoming also increases performance by allowing the selection of the better paths.

8: Why do iBGP peers need to be fully meshed?

** iBGP needs to be fully meshed because it has a fundamental rule stating that iBGP will not propagate back into iBGP a route that it has learned from iBGP. The reason is that this is the only way to prevent routing loops. If each router is connected to every other router (fully meshed), the updates come directly from the source, which removes the need for a router to propagate any updates that it has received.

9: How is a fully meshed network avoided in iBGP?

** A fully meshed network can cause some problems to the routers because they have a great deal of information to handle from every directly connected router. The configuration of route reflectors does not use as much bandwidth, CPU, or memory. Route reflectors allow the router to pass routes on to its peers, and a hub-and-spoke topology is thus possible.

10: What is the equation to determine the number of sessions needed in a fully meshed BGP network?

** The equation for determining the number of sessions required is n (n – 1) / 2, where n is the number of routers. Thus, 10 routers would mean 10 (10 – 1) / 2 = 10 * 9 / 2 = 45 sessions.

Chk out Gauthami @ V V

2006-11-29T13:22:00.000+05:30

Hi frenz,

Surprise still from Vettaiyadu Vilayadu , see the lady (Gauthami) back side of kamal gee...

Switch Port Configuration

2006-11-28T12:56:00.000+05:30

1.Put the following Ethernet standards in order of increasing bandwidth:

802.3z
802.3ae
802.3
802.3u
Answer: c, d, a, b

2.What benefits does switched Ethernet have over shared Ethernet?

Answer: Switched Ethernet ports receive dedicated bandwidth, have a reduced collision domain, and show increased performance because of segmentation or fewer users per port.

3.When a 10/100 Ethernet link is autonegotiating, which will be chosen if both stations can support the same capabilities10BASE-T full duplex, 100BASE-TX half duplex, or 100BASE-TX full duplex?

Answer: 100BASE-TX full duplex will be chosen because it has the highest autonegotiation priority and is common to both end stations.

4.How many pairs of copper wires does a 1000BASE-T connection need?

Answer:Four pairs

5.A switch port is being configured as shown here. What command is needed next to set the port to full-duplex mode?

Switch(config)# interface fastethernet 0/13
Switch(config-if)#

Answer: Enter the command duplex full at the prompt.

6.If a full-duplex Gigabit Ethernet connection offers 2 Gbps throughput, can a single host send data at 2 Gbps?

Answer: No, a full-duplex Gigabit Ethernet connection allows only 1 Gbps simultaneously in each direction across the link.

7.Which GBIC would you use for a connection over multimode fiber (MMF)?

Answer:You could use either a 1000BASE-SX or a 1000BASE-LX/LH.

8. A Category 5 cable having only pins 1,2 and 3,6 has been installed and used for a Fast Ethernet link. Can this same cable be used for a migration to Gigabit Ethernet using 1000BASE-T GBICs, assuming that the length is less than 100 m?

Answer: No. 1000BASE-T requires all four pairs of wires to be present.

9. A Catalyst 3560 switch port has been configured for 100 Mbps full-duplex mode, but a link cannot be established. What are some commands that you could use to investigate and correct the problem?

Answer: To see the current state of one or more ports, you could use the show interface command. This would show the ports' speed and duplex modes, and whether a link has been established. One reason the link is not established could be that the port is shut down or disabled. To enable the port, use the no shutdown interface-configuration command. Because the port has been set to 100 Mbps full-duplex mode, it is possible that the end station can support only 10 Mbps at half duplex. Therefore, set the port for autonegotiate mode with the speed auto and duplex auto commands. Otherwise, you could set the port to a fixed speed and mode that would match that of the end station.

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2006-11-24T13:44:00.000+05:30

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Basics Q & A {Switching}

2006-11-23T13:46:00.000+05:30

1) What is unicast and how does it work?

** Unicast is a one-to-one transmission method. A single frame is sent from the source to a destination on a network. When this frame is received by the switch, the frame is sent on to the network, and the network passes the frame to its destination from the source to a specific destination on a network.

2) What is multicast and how does it work?

** Multicast is a one-to-many transmission method. A single frame is sent from the source to multiple destinations on a network using a multicast address. When this frame is received by the switch, the frame is sent on to the network and the network passes the frame to its intended destination group.

3: What is broadcast and how does it work?

** Broadcast is a one-to-all transmission method. A single frame is sent from the source to a destination on a network using a multicast address. When this frame is received by the switch, the frame is sent on to the network. The network passes the frame to all nodes in the destination network from the source to an unknown destination on a network using a broadcast address. When the switch receives this frame, the frame is sent on to all the networks, and the networks pass the frame on to all the nodes. If it reaches a router, the broadcast frame is dropped.

4: What is fragmentation?

** Fragmentation in a network is the breaking down of a data packet into smaller pieces to accommodate the maximum transmission unit (MTU) of the network.

5:What is MTU? What's the MTU for traditional Ethernet?

** MTU is the acronym for maximum transmission unit and is the largest frame size that can be transmitted over a network. Messages longer than the MTU must be divided into smaller frames. The network layer (Layer 3) protocol determines the MTU from the data link layer (Layer 2) protocol and fragments the messages into the appropriate frame size, making the frames available to the lower layer for transmission without further fragmentation. The MTU for Ethernet is 1518 bytes.

6: What is a MAC address?

** A MAC address is the physical address of a network device and is 48 bits (6 bytes) long. MAC addresses are also known as physical addresses or hardware addresses.

7) What is the difference between a runt and a giant, specific to traditional Ethernet?

** In Ethernet a runt is a frame that is less than 64 bytes in length, and a giant is a frame that is greater than 1518 bytes in length. Giants are frames that are greater than the MTU used, which might not always be 1518 bytes.

8: What is the difference between store-and-forward and cut-through switching?

** Cut-through switching examines just the frame header, determining the output switch port through which the frame will be forwarded. Store-and-forward examines the entire frame, header and data payload, for errors. If the frame is error free, it is forwarded out its destination switch port interface. If the frame has errors, the switch drops the frame from its buffers. This is also known as discarding the frame to the bit bucket.

9: What is the difference between Layer 2 switching and Layer 3 switching?

* * Layer 2 switches make their forwarding decisions based on the Layer 2 (data link) address, such as the MAC address. Layer 3 switches make their forwarding decisions based on the Layer 3 (network) address.

10: What is the difference between Layer 3 switching and routing?

** The difference between Layer 3 switching and routing is that Layer 3 switches have hardware to pass data traffic as fast as Layer 2 switches. However, Layer 3 switches make decisions regarding how to transmit traffic at Layer 3 in the same way as a router. A Layer 3 switch cannot use WAN circuits or use routing protocols; a router is still required for these functions.

Implementing Redistribution & Controlling Routing Updates

2006-11-21T12:59:00.000+05:30

1) State two of the methods that Cisco recommends for controlling routing protocol traffic.

** The methods that Cisco discusses as useful methods of controlling routing updates are as follows:
- Passive interfaces: Prevent routing protocol communication and thus an adjacency from being formed with neighboring routers.
- Changing the administrative distance on the route: Changes the natural order as laid down by Cisco on which routing protocol is more plausible than the others. A scale of weighting is applied to the protocols.
- Default routes: Instruct the router on where to send the destination traffic if the routing table has no entry for that destination.
- Static routes: Offers the ability to configure manually the path to a destination network.
- Route update filtering: Offers the use of access lists to control the exchange of routing information

2) What is the default administrative distance for RIP?

* * The administrative distance for RIP is 120; it has the highest distance of interior routing protocols and is therefore the least likely to be selected.

3) State two instances when you do not want routing information propagated.

** The two occasions that you do not want routing information to be propagated are as follows:
- If there is a WAN link where the cost of the link is based on network traffic. This might also have the added disincentive of being a WAN link that is a dial-on-demand link, which is raised and maintained by the presence of traffic attempting to flow across the interface.
- When you are trying to prevent routing loops. If the routing domain has redundant paths that will be learned by different routing protocol, it is advisable to filter the propagation of one of the paths.

4) In what instances will EIGRP automatically redistribute?

* * EIGRP will automatically redistribute between itself and IGRP as long as both processes are running the same autonomous system number.
EIGRP for IPX automatically redistributes; IPX RIP/SAP and Enhanced IGRP for AppleTalk similarly redistribute automatically into RTMP.

5) Which command is used to view the administrative distance of a route in the routing table?

** The command show ip route displays the administrative distance for each route; two numbers are shown in brackets: the route metric, followed by the administrative distance.

6) When is redistribution required?

** Redistribution is required when there is more than one routing protocol for IP running within the organization and when every part of the network needs connectivity to all the networks.

7) Why does Cisco recommend that you not overlap routing protocols?

** The reason not to overlap routing protocols is that it will increase network traffic, router CPU processing, and memory because of the additional protocol updates. This additional traffic and CPU and memory requirements complicate the routing process. The decision is not simply between multiple paths, but also between the various routing protocols that are advertising them.

8) What is the metric used for in a routing protocol?

** The metric is used to select the best path when multiple paths are available to a remote network.

9) Which has a lower administrative distance, IGRP or OSPF?

** IGRP has an administrative distance of 100, whereas OSPF has an administrative distance of 110. The IGRP path will be entered into the routing table if there are paths offered to the same destination from both protocols.

10) What is the purpose of administrative distance?

** When the routing table is populated with networks that are provided by multiple routing protocols, the administrative distance is used to choose the best path to the remote network.

Super Star Exclusive photo collections

2006-11-20T15:32:00.000+05:30

Basics of BGP

2006-11-19T18:03:00.000+05:30

1:If the weight attribute is used, is a higher or lower weight preferred?

** The weight attribute is proprietary to Cisco and is determined locally on the router. The preference in selection is to the highest weight on the router.

2: What is an alternative to using BGP as the method of connection to the ISP?

** The alternative method, suggested by Cisco, is to use a default route into the ISP and for the ISP to configure static routes into your autonomous system.

3: What does the command clear ip bgp * achieve, and why should it be used cautiously?

** The command resets BGP peer associations, clears the BGP routing table, and reestablishes BGP connections to the neighbors. It should be used cautiously because the loss of connections will drop packets.

4: Give three situations in which you should not use BGP to connect to the Internet.

** It is ill-advised to use BGP in certain conditions:

- When the company has only one connection into the Internet

- When there are limited resources on the network

- When the user is not familiar with BGP configurations or policy-based routing

- When the routers do not understand or need to have greater understanding of each other

5: Explain the use of the command neighbor 10.10.10.10 remote-as 250.

** The command tells the router the IP address of the BGP neighbor and the autonomous system to which the neighbor belongs. This information allows the router to create a TCP session with the neighboring router and exchange BGP routing information.

6: Explain briefly the purpose of the community attribute.

** The community attribute is used to identify prefixes that have some common similarity, without regard to geographic location.

7: In the route selection process, place the following in order of preference: origin code, weight, local preference, and MED. State the method of selection for the individual attributes themselves.

** The correct order is: highest weight, highest local preference, lowest origin code, and lowest MED.

8: What is a mandatory attribute?

** A mandatory attribute is an attribute that is well known. It contains information required in BGP messages in order to maintain the BGP network. These attributes are required and therefore recognized by all BGP implementations.

9: What type of routing protocol is BGP classified as, and what does this mean?

** BGP is classified as an External Gateway Protocol (EGP), as opposed to OSPF, EIGRP, RIP, and so on, which are known as Interior Gateway Protocols (IGPs). If required, BGP can send a summary of the networks known within an organization to maximize security and minimize bandwidth overhead. It is used to convey routing information between autonomous systems.

10: Explain how static routes can be used as an alternative to configuring BGP to connect to another autonomous system.

** A static route could be configured in conjunction with a default route pointing in the other direction. This is a simple solution when there is not a great deal of information to be exchanged between the autonomous systems. A common example is an organization connecting to an ISP.

A static route is a route that has been manually configured. It has the lowest administrative distance of either 0 or 1 by default, depending on the configuration. This means that it will always take precedence over dynamically learned routes and that it must be redistributed into a routing protocol for other routers to make use of it.

11: Explain how a default route can be used as an alternative to configuring BGP to connect to another autonomous system.

** A default route is a route used when there is no entry for the remote network in the routing table. It is used to connect to the Internet and other routing domains when it is not practical to know all the available networks. It is sufficient to have an exit point from your network identified.

12: State two attributes of BGP.

** The following are BGP attributes: next hop, AS_Path, local preference, Multiple Exit Discriminator (MED), community, atomic aggregate, aggregator, and origin.

13: State four message types of BGP.

** The four message types of BGP are:

- Update messages: Contain paths to destination networks and their attributes. Routes that are no longer available or withdrawn routes are included in updates.

- Open messages: Used to establish connections with peers.

- Keepalives: Sent periodically between peers to maintain connections and verify paths held by the router sending the keepalive.

- Notification: Used to inform the receiving router of errors.

14: What is policy-based routing?

** Policy-based routing is the means by which traffic can be forced to take a different route from that determined by the dynamic routing protocol. It is defined on a hop-by-hop basis in that the policy is stated on a router and determines which next hop will be used. The decisions can be based on source and/or destination.

15: What do the letters MED represent? Give a brief explanation of what MED does.

** The Multiple Exit Discriminator is an optional, nontransitive BGP attribute. It is sent only to external BGP peers and is used to influence routers in another autonomous system on the path to take into the autonomous system if multiple paths are available. The lower the value of the attribute, the higher the likelihood that the path will be chosen. By default, a router compares only the MED from routers that are in the same autonomous system as each other but in a different autonomous system from the determining router.

16: What is a community in BGP?

** A community is a group of networks that share a common property. The commonality is defined by the optional transitive attribute, and it has no physical boundaries. A network can be a member of more than one community. When the community is defined, decisions or filtering can be made based on the group instead of the individual.

17: Give two reasons why BGP peer groups are useful.

** A peer group is a group of BGP neighbors that share characteristics. The use of peer groups simplifies the configuration of BGP because one configuration effectively configures every router in the peer group. They are also more efficient because updates are generated once per peer group instead of on a per-router (peer) basis, reducing the resources required to support BGP.

18: What is the difference between a peer and a neighbor?

** In external BGP, there is no difference between a neighbor and a peer. A peer is the BGP term for a neighbor. Both terms refer to a router that is directly connected, with which routing information is exchanged. In iBGP, these routers are not necessarily physically adjacent, but they are the next logical hop router running BGP.

19: In BGP, describe the purpose of the network command.

** The network command permits BGP to advertise a network if it is present in the routing table. It is not responsible for starting the BGP process on an interface; instead, it identifies which networks the router originates.

20: Explain the command neighbor {ip-address | peer-group-name} next-hop-self.

** On a broadcast multiaccess network such as Ethernet, the next-hop address is the IP address of the advertising router. This command forces BGP to advertise itself as the next-hop router instead of letting the protocol determine the address to be used. This avoids problems seen on NBMA networks or nonmeshed environments, such as X.25 and Frame Relay.

Ethernet LAN's-Layer-2 Q & A

2006-11-18T11:25:00.000+05:30

1: What is a MAC address?

** A MAC address is the physical address of a network device and is 48 bits (6 bytes) long. MAC addresses are also known as the physical addresses and hardware addresses.

2: What are the components of a MAC address?

** A MAC address is made up of two parts: the organizational unique identifier (OUI) and the vendor assigned serial number, or address.

3: How is a MAC address represented?

** A MAC address is represented in hexadecimal format, specifically as six pairs of hexadecimal numbers separated by hyphens.

4: How does Ethernet operate?

** Ethernet is a shared media LAN operating at 10-Mbps, 100-Mbps, 1000-Mbps (Gigabit) or 10000-Mbps (10 Gigabit) modes. 10/100 Ethernet and Gigabit Ethernet can operate in either half-duplex or full-duplex mode. 10 Gigabit Ethernet operates in full-duplex mode only. When in half-duplex mode, Ethernet operates in a CSMA/CD environment, whereas in full-duplex mode each device has dedicated access to network bandwidth.

Carrier sense multiple access collision detect (CSMA/CD) enables half-duplex Ethernet operation, in that each device listens to the line before sending its data. If the line is in use, meaning the device senses a carrier on the line, it holds off transmitting. If the line is not in use, meaning no carrier is sensed on the line, the device begins transmitting.

5: What is a collision, and what happens when a collision occurs on an Ethernet network segment?

** A collision occurs when two or more devices attached to an Ethernet network segment send traffic across the line at the same time. When a collision occurs, each affected device waits a random amount of time before resending the data. The length of the wait is determined by a backoff algorithm.

6: Describe a repeater and how it operates.

** A repeater repeats incoming signals from one interface and regenerates, or resends, the signal out all other interfaces.

7: Describe a hub and how it operates.

** A hub is a central device in a network that joins lines together in a star configuration. Ethernet hubs are multiport repeaters often with 4, 8, 16, or 24 ports. A signal received on one port is repeated out all ports to all connected devices; it is up to each device to determine by the destination MAC address if it is the intended recipient of the transmission.

8: Describe a bridge and how it operates.

** A bridge is a multiport hub and is used to connect two or more LAN segments together. A bridge uses a filtering table to determine whether a frame received from one LAN segment is to be filtered (dropped) or forwarded to another LAN segment connected to the bridge.

9: Describe a switch and how it operates.

** A switch is a multiport bridge that cross connects two LAN nodes together, giving each sender/receiver pair the full network bandwidth rather than the shared bandwidth environment created by hubs. Switches separate collision domains by filtering and forwarding frames based on the source and destination hardware, or MAC, addresses. When a switch receives frames destined for an unknown address, the switch broadcasts these frames out all ports.

10: Describe a router and how it operates.

** Routers are devices that forward data packets from one local-area network (LAN) or wide-area network (WAN) to another LAN or WAN. Routers forward these packets based on their routing tables, which are built using certain routing protocols. Routers read the network address from the packet within each transmitted frame and select a transmission method for the packet based on the best route available. Routers also drop packets destined for an unknown address. An unknown address is an address that is not found in the routing tables.

11: What is a backoff algorithm?

** The backoff algorithm is a random amount of time each station waits after a collision has occurred on the network segment before attempting data retransmission.

12: What Ethernet technologies operate in half-duplex mode? Full-duplex mode?

** Half-duplex: 10 Mbps (10BASE-T), 100 Mbps (100BASE-T), 1000 Mbps (Gigabit Ethernet). Full-duplex: 10 Mbps (10BASE-T), 100 Mbps (100BASE-T), 1000Mbps (Gigabit Ethernet), 10000 Mbps (10 Gigabit Ethernet). 10-Mbps and 100-Mbps Ethernet can operate in either half-or full-duplex mode depending on the network interface card and switch port capability.

13: Given the MAC address 00-aa-00-62-c6-09, identify the OUI and vendor-assigned serial number.

* * OUI: 00-aa-00

Serial number: 62-c6-09

14: How does a bridge determine whether a frame is forwarded or filtered?

** Bridges determine whether to forward a frame based on the entries in its filtering table. If a frame is received from a port and the frame is destined for the network segment on that same port, the bridge filters (drops) the frame from its memory because the intended recipient is on the same network segment and would have received the frame. If the destination network segment is on a different bridge port, the bridge forwards the frame out that intended port.

15: What is the difference between cut-through and store-and-forward switching?

** Cut-through switching forwards an incoming data frame before the frame is completely received by the switch. Store-and-forward switching stores the complete incoming frame before forwarding the frame on to its intended destination.

16: In what LAN environment are routers most commonly used?

** In a local-area network (LAN) environment a router is commonly used to connect LANs together across a wide-area network (WAN) or to connect a LAN to the Internet.

IP Routing Principles

2006-11-17T12:22:00.000+05:30

1: In the routing table, a field indicates the source of the routing information. If the field showed the letter C, what would this mean?

** A field showing the letter C would mean that the network is directly connected.

2: In the routing table, how is the next hop indicated?

** In the routing table, the next hop is indicated by the word via followed by an IP address. This is the address of the next logical hop.

3: Cisco distinguishes between the routing and the switching functions. What is the difference?

** The routing function is how the router learns the logical topology of the network. It decides whether the datagram can be routed, which path to select if there is a choice, and to which outgoing interface to queue the datagram. It operates at Layer 3 of the OSI stack.

The switching function is the forwarding of the frame from the inbound interface to an outbound interface. It operates at Layer 2 of the OSI stack, not at Layer 3 like a router, because the routing or Layer 3 function has already been completed.

4: Name the interior IP routing protocols that send the mask with the routing update.

** The interior IP routing protocols that send the mask with the routing update are EIGRP, OSPF, IS-IS, and RIPv2.

5: Does VLSM require a classful or classless routing protocol, and why?

** VLSM requires a classless routing protocol because it needs the subnet mask to be sent with the update.

6: State one of the characteristics of a classful routing protocol.

** The characteristics of a classful routing protocol are as follows:

- It summarizes at the network boundary.

- Routes exchanged between foreign networks are summarized to the NIC number.

- Within the same network (IANA classful network), subnet routes are exchanged by routers.

- All the interfaces on all the routers within a NIC number must share the same subnet mask.

- VLSM is not possible within the network

7: What is the command to show whether a specific network, such as 141.131.6.16, is present in the routing table?

** The command to show whether a specific network, such as 141.131.6.16, is present in the routing table is as follows:
show ip route 141.131.6.16

8: State one major difference between a classful protocol and a classless routing protocol.

** Major differences between classful and classless routing protocols include:

- The capability to use VLSM

- The capability to summarize at an administratively defined boundary, as opposed to summarizing at the classful boundary

- The capability to maximize the logical address space

9: Describe briefly the difference between a routing and routed protocol.

** The routed protocol is the Layer 3 protocol used to transfer data from one end device to another across the network. The routed protocol is the Layer 3 datagram that carries the application data in addition to the upper-layer information.

The routing protocol is the protocol used to send updates between the routers about the networks that exist in the organization, thereby allowing the routing process to determine the path of the datagram across the network.

10: Describe the processes used to build and maintain the routing table.

** There are three steps involved in building and maintaining the routing table. These three processes are independent and include:

The routing protocol, which actually sends the information about the routes or networks within the autonomous system, such as RIPv1, IGRP, EIGRP

The routing table, which receives updates from the routing protocol and provides the forwarding process with information on request

The forwarding process, which determines which path to select from the routing table in order to forward a datagram

11: Give a brief explanation of the switching function.

** The switching function does the following:

- Checks the incoming frame for validity

- Checks whether the frame is addressed (at Layer 2) to the router

- Checks whether the frame is within the scope of the framing criteria (too big or too small)

- Checks whether the frame passes CRC

- Strips the Layer 2 header and trailer from the frame and checks the destination address against the cache entries

- Creates the appropriate frame header and trailer (if there is an entry in cache for the destination address) and forwards the frame to the outbound interface queue

12: What information is contained in the fast switching cache?

** If fast switching is enabled, the datagram is then examined again, and an entry is put into a route cache. The entry in this cache consists of the following:

- An IP prefix

- The output interface

- The link-layer header to be used in forwarding the datagram

13: When would you use the command no auto-summary?

** Some routing protocols, such as BGP, RIPv2, and EIGRP, summarize at the network boundary automatically. Summarization within the NIC number boundary must be configured manually, and therefore autosummarization must first be disabled with the no auto-summary command.

14: When does OSPF send updates, and do they contain the entire routing table?

** Each OSPF router refreshes its LSA every 30 minutes. An LSA will be sent earlier if there is an adjacency change.

15: Network convergence is when a network domain has learned about the new network topology after a change has occurred in the domain. What is considered a network change that would require network convergence?

** The accuracy of the table will be affected by how quickly it responds to changes in the network. These changes include the following:

- Learning new networks

- Learning a better path to an existing network

- Learning that a network is no longer available

- Learning an alternative route to a network

16: When would you consider using a static route in your network?

** A static route would be configured for the following reasons:

- Links that have very low bandwidth, such as dialup links

- The administrator needs control over the link

- The link is a backup to the dynamically learned route

- There is only one path to the remote network, such as a stub network

- The router has very limited resources and cannot run a routing protocol

- The administrator needs to control the routing table to allow a classful protocol and a classless routing protocol to populate the routing table

17: When would you consider using a default route in your network?

** Occasions for using a default route include:

- Connecting to the autonomous system from a stub network

- Connecting to the Internet

18: What command is used to configure ODR on a hub router?

** router odr is the only command needed to be configured on the hub router.

19: When would you consider using a floating static route in your network?

** Floating static routes are used when a backup route is required.

20: Describe some of the characteristics of classless routing protocols.

** Classless routing protocols include OSPF, EIGRP, RIPv2, IS-IS, and BGP.

- The characteristics of a classless routing protocol are:

- Router interfaces within the same network can have different subnet masks (VLSM).

- They support the use of classless interdomain routing (CIDR).

- Some routes can be summarized within the major NIC number. This is done manually.

OSPF Q & A in CCNP

2006-11-16T11:54:00.000+05:30

1: What information is held in the topology table?

** The topology table holds a map of every link in the area. Every topology table in the area is the same. This is sometimes referred to as the link-state database.

2: What command is used to determine manually which router on a LAN will become the DR?

** The ip ospf priority number command is used to determine the DR manually. The higher the priority, the greater the likelihood is of success.

3: How many subnets are required in an OSPF configuration over a point-to-point network that has multiple connections?

** It is necessary to have one subnet per connection. Thus, if there are four point-to-point links, four subnets are required.

4: State the different types of packets used to build a routing table for the first time.

** Five packets are used to build the routing table for the first time:

- The hello packet— This is used to find neighbors and to determine the designated and BDR. The continued propagation of the hello packet maintains the transmitting router in the topology database of those that hear the message.
- The database descriptor— This is used to send summary information to neighbors to synchronize topology databases.
- The LSR— This is a request for more detailed information, which is sent when the router receives a database descriptor that contains new information.
- The LSU— This is the LSA packet issued in response to the request for database information in the LSR packet.
- The link-state acknowledgement— This acknowledges the LSU.

5: In creating an adjacency, what is the exstart state?

** The exstart state is a stage in the forming of an adjacency between neighbors. This stage is the stage when the DR and the BDR have been elected. The master/slave relationship has been established, as has the initial sequence number of the DDP packets.

6: What is the database descriptor and when is it used?

** Referred to as DBDs or database descriptor packets (DDPs), these are packets exchanged between neighbors during the exchange state. The DDPs contain summary information taken from the LSAs, which describe the links of every router in the neighbor's topology table.

7: Explain the difference between an LSR and an LSA.

** A link-state advertisement (LSA) is a packet describing a router's links and the state of those links. There are different types of LSAs to describe the different types of links.
An LSR is a link-state request, which is used when the router receives a DDP complete with summary information taken from the LSA. It compares the LSA against the topological database. If either the LSA entry is not present or the entry is older than the DDP, it will request further information via an LSR.

8: What packet is used to maintain the neighbor table?

** The hello packet is used to maintain the neighbor table. Whenever a hello is heard, the source address in the hello packet is used to reset the hello interval timer. This shows that the neighbor is still active.

9: What is the metric used by OSPF standards? Is this the same metric that Cisco uses?

** OSPF defines cost as the OSPF metric, but does not define what cost represents. Thus, any determinant could be used and defined manually as cost. Cisco has set a default metric to be the inverse of bandwidth, making the fastest link the most preferred link. This default can be overridden by manual configuration.

10: Explain the meaning of the letters BDR.

** BDR stands for backup designated router. This router acts as the backup to the DR in case the DR fails. The BDR performs none of the DR functions while the DR is operating correctly.

OSPF Q & A in CCNP

2006-11-14T16:40:00.000+05:30

1: Which command in OSPF shows the network LSA information?

** The command show ip ospf [process-id area-id] database network displays the network link-state information.

2: What command would you use to create a totally stubby area?

** The command area area-id stub no-summary will create a totally stubby area. This is a subcommand to the router ospf process-id command. It is necessary only on the ABR, but all the other routers in the area must be configured as stub routers.

3: What is a virtual link, and what command would you use to create it?

** A virtual link is a link that creates a tunnel through an area to the backbone (Area 0). This allows an area that cannot connect directly to the backbone to do so virtually. The command to create the link is area area-id virtual-link router-id. Note that the area-id that is supplied is that of the transit area, and the router-id is that of the router at the other end of the link. The command needs to be configured at both ends of the tunnel.

4: Where would you issue the command to summarize IP subnets? State the command that is used.

** Summarization is done at area boundaries. The command to start summarization is the area range command, with the syntax area area-id range address mask. To summarize external routes, use the summary-address command on the ASBRs.

5: How would you summarize external routes before injecting them into the OSPF domain?

** The command summary-address address mask is the command that you would use.

6: When is a virtual link used?

** A virtual link is used when an area is not directly attached to the backbone area (Area 0). This may be due to poor design and a lack of understanding about the operation of OSPF, or it may be due to a link failure. The most common cause of an area separating from the backbone is link failure, which can also cause the backbone to be segmented. The virtual link is used in these instances to join the two backbone areas together. Segmented backbone areas might also be the result of two companies merging.

7: Give the command for defining the cost of a default route propagated into an area.

** The command to define the cost of a default route propagated into another area is area area-id default-cost cost.

8: Give an example of when it would be appropriate to define a default cost.

** It is appropriate to define a default cost for the default route when a stub area has more than one ABR. This command allows the ABR or exit point for the area to be determined by the network administrator. If this link or the ABR fails, the other ABR will become the exit point for the area.

9: On which router is the area default cost defined?

** The default cost for the default route is defined on the ABR. The ABR will then automatically generate and advertise the route cost along with the default route.

10: Give the command to configure a stub area and state on which router it is configured.

** The command syntax to configure a stub area is area area-id stub. This command is configured on the ABR connecting to the area and on all the routers within the area. Once the configuration is completed, the Hellos are generated with the E bit set to 0. All routers in the area will only form adjacencies with other routers that have the E bit set.

11: What is the purpose of the area range command, and why is it configured on the ABR?

** The area range command is configured on an ABR because it dictates the networks that will be advertised out of the area. It is used to consolidate and summarize the routes at an area boundary.

12: Give the commands to configure a router to place subnets 144.111.248.0 through to 144.111.255.0 in Area 1 and to put all other interfaces into Area 0.

** The commands are as follows:

network 144.111.248.0 0.0.7.255 area 1

network 0.0.0.0 255.255.255.255 area 0

13: Give the syntax to summarize the subnets 144.111.248.0 to 144.111.254.255 into another autonomous system.

** The syntax is as follows:

summary-address 144.111.248.0 255.255.248.0

14: Explain briefly the difference between the area range command and the summary-address command.

** The area range command is used to summarize networks between areas and is configured on the ABR. The summary-address command is used to summarize networks between autonomous systems and is configured on the ASBR.

15: Explain the following syntax and what it will achieve: area 1 stub no-summary.

** The command area 1 stub no-summary creates a totally stubby area. The number after the word area indicates the area that is being defined as a totally stubby area. This is necessary because the router might be an ABR with connections to many areas. Once this command is issued, it prevents summarized and external routes from being propagated by the ABR into the area. To reach the networks and hosts outside the area, routers must use the default route advertised by the ABR into the area.

16: Why would you configure the routing process to log adjacency changes as opposed to turning on debug for the same trigger?

** The reason to configure the router process to log adjacency changes to syslog as opposed to running debug is an issue of resources. It takes fewer router and administrator resources to report on a change of state as it happens than to have the debugger running constantly. The debug process has the highest priority and thus everything waits for it.

17: Give some of the common reasons that neighbors fail to form an adjacency.

** Many OSPF problems stem from adjacency problems that propagate throughout the network. Many problems are often traced back to neighbor discrepancies.

If a router configured for OSPF routing is not seeing an OSPF neighbor on an attached network, do the following:

- Make sure that both routers are configured with the same IP mask, MTU, Interface Hello timer, OSPF Hello interval, and OSPF dead interval.

- Make sure that both neighbors are part of the same area and area type.

- Use the debug and show commands to trace the problem.

18: When configuring a virtual link, which routers are configured?

** The configuration is between the ABRs, where one of the ABRs resides in Area 0 and the other in the area that is disconnected from the backbone. Both of the ABRs are also members of the transit area. Having created the virtual link, both ABRs are now members of Area 0, the disconnected area, and the transit area.

19: What does the command area 1 default-cost 15 achieve?

** The command area 1 default-cost 15 will assign a cost of 15 to the default route that is to be propagated into the stub area. This command is configured on the ABR attached to the stub area.

20: Explain what is placed in the parameters area-id and router-id for the command area area-id virtual-link router-id.

** The parameter area-id is the area ID of the transit area. So if the ABR in Area 0 is creating a virtual link with the ABR in Area 3 through Area 2, the area ID stated in the command is Area 2. The router ID is the router ID of the router with whom the link is to be formed and a neighbor relationship and adjacency established.

Classes of IP addresses

2006-11-13T21:00:00.000+05:30

1. To which class of IP address would the IP address of 197.22.103.221 belong?

A. class "A"
B. class "B"
C. class "C"
D. class “D”
E. class “E”

2. Which of the following dotted notations cannot represent an IP address?

A. 301.188.12.77
B. 167.78.35.202
C. 122.31.22.226
D. 254.254.254.254

3. In a class "A" network using an IP addressing scheme, the first sixteen bits are used for the network part of the address, and the last two octets are reserved for the host part of the address.

A. True
B. False

4. To what class of network would the following IP address belong: 144.26.108.15?

A. Class "A" network
B. Class "B" network
C. Class "C" network
D. Class “D” network

5. To what class of network would the IP address, 18.12.245.10, belong?

A. Class "A" network
B. Class "B" network
C. Class "C" network
D. Class “D” network

6. In the IP address, 190.233.21.12, how many octets have been assigned by the NIC?

A. One
B. Two
C. Three
D. Four

7. In the IP address, 88.224.73.201, how many octets could be assigned locally by the network administrator?

A. One
B. Two
C. Three
D. Four

8. Select the IP address below which would belong to the largest network.

A. 69.22.214.158
B. 144.144.144.3
C. 220.91.144.222
D. 255.255.255.255

9. Which of the following best describes a class "B" network?

A. network.network.host.host
B. network.network.network.host
C. network.host.host.host
D. host.network.host.network

10. There are three classes of commercial networks.

A. False
B. True

11. Which of the following is an example of a class "C" network address?

A. 196.25.10.0
B. 113.0.0.0
C. 11.3.22.104.0
D. 74.255.255.255

12. Which of the following best describes a class “C” network?

A. network.network.host.host
B. network.network.network.host
C. network.host.host.host
D. host.host.host.network

13. Which of the following best describes a class “A” network?

A. network.network.host.host
B. network.network.network.host
C. network.host.host.host
D. host.host.host.network

14. Which of the following is a class “C” IP address?

A. 220.15.64.126
B. 191.15.64.126
C. 127.15.64.126
D. 242.15.64.126

15. Select the IP address for the smallest network.

A. 220.15.64.126
B. 191.15.64.126
C. 127.15.64.126
D. 242.15.64.126

16. How many octets have been assigned by InterNIC in a class “C” network?

A. one
B. two
C. three
D. four

17. If you have a class “A” IP address, then how many bytes have been assigned to you for your hosts?

A. one
B. two
C. three
D. four

V-LAN

2006-11-09T16:38:00.000+05:30

1. What is a VLAN? When is it used?

Answer: A VLAN is a group of devices on the same broadcast domain, such as a logical subnet or segment. VLANs can span switch ports, switches within a switch block, or closets and buildings. VLANs group users and devices into common workgroups across geographical areas. VLANs help provide segmentation, security, and problem isolation.

2. When a VLAN is configured on a Catalyst switch port, in how much of the campus network will the VLAN number be unique and significant?

Answer: The VLAN number will be significant in the local switch. If trunking is enabled, the VLAN number will be significant across the entire trunking domain. In other words, the VLAN will be transported to every switch that has a trunk link supporting that VLAN.

3. Name two types of VLANs in terms of spanning areas of the campus network.

Answer: Local VLAN
End-to-end VLAN

4. What switch commands configure Fast Ethernet port 4/11 for VLAN 2?

Answer: interface fastethernet 4/11
switchport mode access
switchport access vlan 2

5. Generally, what must be configured (both switch and end-user device) for a port-based VLAN?

Answer: The switch port

6. What is the default VLAN on all ports of a Catalyst switch?

Answer: VLAN 1

7. What is a trunk link?

Answer: A trunk link is a connection between two switches that transports traffic from multiple VLANs. Each frame is identified with its source VLAN during its trip across the trunk link.

8. What methods of Ethernet VLAN frame identification can be used on a Catalyst switch trunk?

Answer: 802.1Q
ISL

9. What is the difference between the two trunking methods? How many bytes are added to trunked frames for VLAN identification in each method?

Answer: ISL uses encapsulation and adds a 26-byte header and a 4-byte trailer. 802.1Q adds a 4-byte tag field within existing frames, without encapsulation.

10. What is the purpose of the Dynamic Trunking Protocol (DTP)?

Answer: DTP allows negotiation of a common trunking method between endpoints of a trunk link.

11. What commands are needed to configure a Catalyst switch trunk port Gigabit 3/1 to transport only VLANs 100, 200 through 205, and 300 using IEEE 802.1Q? (Assume that trunking is enabled and active on the port already. Also assume that the interface gigabit 3/1 command already has been entered.)

Answer: switchport trunk allowed vlan 100, 200-205, 300

12. Two neighboring switch trunk ports are set to the auto mode with ISL trunking encapsulation mode. What will the resulting trunk mode become?

Answer: Trunking will not be established. Both switches are in the passive auto state and are waiting to be asked to start the trunking mode. The link will remain an access link on both switches.

13. Complete the following command to configure the switch port to use DTP to actively ask the other end to become a trunk:
switchport mode _________________

Answer: switchport mode dynamic desirable

14. Which command can set the native VLAN of a trunk port to VLAN 100 after the interface has been selected?

Answer: switchport trunk native vlan 100

15. What command can configure a trunk port to stop sending and receiving DTP packets completely?

Answer: switchport nonegotiate

16. What command can be used on a Catalyst switch to verify exactly what VLANs will be transported over trunk link gigabitethernet 4/4?

Answer: show interface gigabitethernet 4/4 switchport
or
show interface gigabitethernet 4/4 switchport trunk

17. Suppose that a switch port is configured with the following commands. A PC with a nontrunking NIC card then is connected to that port. What, if any, traffic will the PC successfully send and receive?

interface fastethernet 0/12
switchport trunk encapsulation dot1q
switchport trunk native vlan 10
switchport trunk allowed vlan 1-1005
switchport mode trunk

Answer: The PC expects only a single network connection, using a single VLAN. In other words, the PC can't participate in any form of trunking. Only untagged or unencapsulated frames will be understood. Recall that an 802.1Q trunk's native VLAN is the only VLAN that has untagged frames. Therefore, the PC will be capable of exchanging frames only on VLAN 10, the native VLAN.

Networking Basics

2006-11-08T15:22:00.000+05:30

1: What is the definition of a network?

** A network is a system of lines or channels that cross or interconnect, or a group or system of electrical components and connecting circuitry designed to function in a specific manner.

2: What are network models?

** Network models provide the guiding principles behind the development of network standards.

3: What is a network standard, and why are there network standards?

** Network standards define the rules of network communication and are like laws that must be followed for different equipment vendors to work together.

4: What is a proprietary feature?

** If a vendor implements a feature that does not adhere to any network standards, it is called a proprietary feature.

5: What are the three data transmission modes, and how do they operate?

** Simplex mode, half-duplex mode, and full-duplex mode. Simplex mode is one-way communication only. Half-duplex mode is two-way communication, but not at the same time. Full-duplex mode is simultaneous two-way communication.

6: List the major characteristics of a LAN.

** The primary characteristic of a LAN is its geographic coverage. LANs are found in a small geographic area where there is a short distance between connected computers, as in small offices or on each floor of a larger office building. LANs enable the sharing of office resources, such as file servers for file sharing among users or print servers for shared printers.

7: List the major characteristics of a MAN.

** MANs are found in a metropolitan, or citywide, geographic area, interconnecting two or more office buildings in a broader geographic region than a LAN would support, but not so broad that a WAN would be required.

8: List the major characteristics of a WAN.

** WANS are found in broad geographic areas, often spanning states and countries, and are used to connect LANs and WANs together.

9: What are the three parts of a frame? What is a function of each part?

** Header, data (or payload), trailer. The header is the beginning of the frame, significant in that the frame's source and destination are found in the frame header. The payload is the data part of the frame, the user's information. The trailer identifies the end of the frame.

10: What function in a network does cabling provide?

** Cabling provides the physical interconnection between network devices and nodes.

11: List some examples of user data.

** Examples of user data include e-mail, web-browsing traffic, word-processed documents, spreadsheets, database updates.

12: What is the best definition of network topology?

** Network topology refers to the physical or logical geometric arrangement of interconnected network devices.

13: What is the best definition of network protocol?

** A network protocol is the communication rules and formats followed by all interconnected devices on a network requiring communication with one another.

14: What is the definition of network media?

** Network media refers to the physical component of a network. Communication signals traverse network media from source to destination. Some examples of network media are copper and fiber-optic cabling.

15: What is a network origination point?

** A network connection has two ends: the origination and termination points. The origination point is the source of the data—the location from which the data is being sent.

16: What is a network termination point?

** A network connection has two ends: the origination and termination points. The termination point is the destination of the data—the location to which the data is being sent.

Layer 3 Switching

2006-11-07T16:09:00.000+05:30

1. What might you need to implement interVLAN routing?

** One or more Layer 3 interfaces

One or more SVIs

Static routes

A dynamic routing protocol

2. Can interVLAN routing be performed over a single trunk link?

** Yes. Packets can be forwarded between the VLANs carried over the trunk.

3. To configure an SVI, what commands are needed?

** First, make sure the VLAN is defined on the switch.

interface vlan vlan-id
ip address ip-address mask
no shutdown

4. What command can verify the VLAN assignments on a Layer 2 port?

** show interface type mod/num switchport

or

show interface status

5. A switch has the following interface configurations in its running configuration:

interface fastethernet 0/1
switchport access vlan 5
!
interface vlan 5
ip address 192.168.10.1 255.255.255.0
no shutdown

What is necessary for packets to get from the FastEthernet interface to the VLAN 5 SVI?

Answer: Nothing. Both are assigned to VLAN 5, so normal Layer 2 transparent bridging will take care of all forwarding between the two.

6. What is the source of FIB information?

** The routing table, as computed by the Layer 3 engine portion of a switch.

7. How often is the FIB updated?

** As needed. It is downloaded or updated dynamically by the Layer 3 engine whenever the routing topology changes or an ARP entry changes.

8. What is meant by the term "CEF punt"?

** A packet can't be forwarded or switched by CEF directly because it needs further processing. The packet is "punted" to the Layer 3 engine, effectively bypassing CEF for a more involved resolution.

9. What happens to the FIB when distributed CEF (dCEF) is used?

** It is simply replicated to each of the independent CEF engines. The FIB itself remains intact so that each engine receives a duplicate copy.

10. What happens during a "CEF glean" process?

** The MAC address (ARP reply) for a next-hop FIB entry is not yet known. The Layer 3 engine must generate an ARP request and wait for a reply before CEF forwarding can continue to that destination.

11. What does a multilayer switch do to the IP TTL value just before a packet is forwarded?

** The TTL is decremented by one, as if a router had forwarded the packet.

12. What is fallback bridging?

** On switch platforms that cannot multilayer-switch (route) all routable protocols, those protocols can be bridged transparently between VLANs instead.

13. Is it possible for an SVI to go down? If so, for what reasons?

** Yes. The SVI can be shut down administratively with the shutdown command, as with any other interface. Also, if the VLAN associated with the SVI is not defined or active, the SVI will appear to be down.

Integrated IS - IS

2006-11-06T20:14:00.000+05:30

1: What is an intermediate system?

** An Intermediate System is the ISO term for a router.

2: What is a network protocol data unit?

** A Network Protocol Data Unit is the ISO term for a packet.

3: What is the difference between an L1, an L2, and an L1/L2 router?

** An L1 router has no direct connections to another area. An L2 router only routes inter-area traffic. An L1/L2 router routes both inter-area and intra-area traffic and acts as an inter-area gateway for L1 routers.

4: Explain the basic difference between an IS-IS area and an OSPF area.

** The borders of IS-IS areas are between routers, on links. The borders of OSPF areas are defined by the routers themselves.

5: What is a network entity title (NET)?

** The Network Entity Title is an address by which a router identifies both itself and the area in which it resides.

6: To what value must the NSAP Selector be set in a NET?

** The NSAP Selector should be set to 0x00 in a NET.

7: What is the purpose of a System ID?

** The System ID uniquely identifies a router within an IS-IS domain.

8: How does a router determine what area it is in?

** The portion of the NET preceding the last seven octets is the area address.

9: Does IS-IS elect a Backup Designated Router on a broadcast subnetwork?

** IS-IS does not elect a BDR.

10: What is the purpose of the Pseudonode ID?

** The Pseudonode ID is the last octet of a LAN ID. Its purpose is to distinguish LAN IDs which are originated by a single router which is the DR on multiple LANs.

11: What is the maximum age (MaxAge) of an IS-IS LSP?

** The MaxAge of an IS-IS LSP is 1200 seconds (20 minutes).

12: What is the basic difference between the way OSPF ages its LSAs and the way IS-IS ages its LSPs?

** OSPF increments the age up to MaxAge; IS-IS decrements the age down to 0. A new OSPF LSA has an age of 0, whereas a new IS-IS LSP has an age of MaxAge.

13: How often does an IS-IS router refresh its LSPs?

** The refresh rate of an IS-IS router is 900 seconds (15 minutes).

14: What is a Complete Sequence Number Packet (CSNP)? How is it used?

** A Complete Sequence Number Packet contains a full listing of all LSPs in a database. A CSNP is periodically sent by the Designated Router on a broadcast network to maintain database synchronization.

15: What is a Partial Sequence Number Packet (PSNP)? How is it used?

** A Partial Sequence Number Packet contains a listing of one or more LSPs. It has two uses: On point-to-point networks, it is used to acknowledge the receipt of LSPs. On broadcast networks, it is used to request LSPs.

Kamal Photo's

2006-11-06T20:12:00.000+05:30

Kamal From V V

2006-11-06T20:08:00.000+05:30

Dynamic Routing Protocols Part- II

2006-11-05T19:23:00.000+05:30

6: What is a distance vector routing protocol?

* A distance vector protocol is a routing protocol in which each router calculates routes based on the routes of its neighbors and then passes its routes to other neighbors.

7: Name several problems associated with distance vector protocols.

* Several problems associated with distance vector protocols are:

-> A susceptibility to incorrect routing information because of its dependence on neighbors for correct information
-> Slow convergence
-> Route loops
-> Counting to infinity

8: What are neighbors?

* Neighbors are routers connected to the same data link.

9: What is the purpose of route invalidation timers?

* Route invalidation timers delete routes from a route table if they exceed a certain age.

10: Explain the difference between simple split horizon and split horizon with poisoned reverse.

* Simple split horizon does not send route information back to the source of the route information.
Split horizon with poisoned reverse sends the information back to the source but sets the metric to unreachable.

Dynamic Routing Protocols

2006-11-04T16:20:00.000+05:30

1: What is a routing protocol?

* A routing protocol is a "language" that routers speak to each other to share information about network destinations.

2: What basic procedures should a routing algorithm perform?

* At a minimum, a routing protocol should define procedures for:Passing reachability information about networks to other routersReceiving reachability information from other routersDetermining optimal routes based on the reachability information it has and for recording this information in a route tableReacting to, compensating for, and advertising topology changes in an internetwork

3: Why do routing protocols use metrics?

**A route metric, also called a route cost or a route distance, is used to determine the best path to a destination. Best is defined by the type of metric used.

4: What is convergence time?

* Convergence time is the time a group of routers take to complete the exchange of routing information.

5: What is load balancing? Name four different types of load balancing.

* Load balancing is the process of sending packets over multiple paths to the same destination.Four types of load balancing are:
a) Equal cost, per packet
b) Equal cost, per destination
c) Unequal cost, per packet
d) Unequal cost, per destination

RIP , Q & A part ----II

2006-11-04T16:17:00.000+05:30

6: Why is a random timer associated with triggered updates? What is the range of this timer?

* The random timer, whose range is 1 to 5 seconds, prevents a "storm" of triggered updates during a topology change.

7: What is the difference between a RIP Request message and a RIP Response message?

* A Request message asks a router for an update. A Response message is an update.

8: Which two types of Request messages does RIP use?

* A Request message may either ask for a full update or in some special cases it may ask for specific routes.

9: Under what circumstances will a RIP response be sent?

* A Response is sent when the update timer expires, or upon reception of a Request message.

10: Why does RIP hide subnets at major network boundaries?

** RIP updates do not include the subnet mask of the destination address, so a RIP router depends on the subnet masks of its own interfaces to determine how an attached major network address is subnetted. If a router does not have an attachment to a particular major network address, it has no way to know how that major network is subnetted. Therefore, no subnets of a major network address can be advertised into another major network

Static Routing

2006-11-04T13:29:00.000+05:30

1: What information must be stored in the route table?

* At a minimum, each entry of the routing table must include a destination address and the address of a next-hop router or an indication that the destination address is directly connected.

2: What does it mean when a route table says that an address is variably subnetted?

* Variably subnetted means that the router knows of more than one subnet mask for subnets of the same major IP address..

3: What are discontiguous subnets?

* Discontiguous subnets are two or more subnets of a major IP network address that are separated by a different major IP address.

4: What command is used to examine the route table in a Cisco router?

* show ip route is used to examine the routing table of a Cisco router.

5: What are the two bracketed numbers associated with the non-directly connected routes in the route table?

* The first bracketed number is the administrative distance of the routing protocol by which the route was learned. The second number is the metric of the route.

IGRP Q & A

2006-11-01T15:10:00.000+05:30

1: Which UDP port number is used to access IGRP?

*** IGRP does not use a UDP port. It is accessed directly from the network layer, as protocol number 9.

2: What is the maximum IGRP internetwork diameter, in hops?

*** The maximum IGRP network diameter is 255 hops.

3: What is the default update period for IGRP?

*** The default IGRP update period is 90 seconds.

4: Why does IGRP specify an autonomous system number?

*** IGRP specifies an autonomous system number so that multiple IGRP processes can be enabled within the same routing domain and even on the same router.

5: What is the default IGRP holddown time?

** The default IGRP holddown time is 280 seconds.

6: Which variables can IGRP use to calculate its composite metric?

** IGRP can use bandwidth, delay, load, and reliability to calculate its metric. By default, it uses only bandwidth and delay.

7: How many entries can be carried within a single IGRP update packet?

** An IGRP update packet can carry up to 104 route entries.

kamalhasan from V V

2006-11-01T15:01:00.000+05:30

Routing Information Protocol Version 2

2006-10-31T17:09:00.000+05:30

1: Which three fields are new to the RIPv2 message format?

*** The Route Tag field, the Subnet Mask field, and the Next Hop field are RIPv2 extensions that do not exist in RIPv1 messages. The basic format of the RIP message remains unchanged between the two versions; version 2 merely uses fields that are unused in version 1.

2: Besides the extensions defined by the three fields of question 1, what are the other two major changes from RIPv1?

***In addition to the functions that use the new fields, RIPv2 supports authentication and multicast updates.

3: What is the multicast address used by RIPv2? What is the advantage of multicasting messages over broadcasting them?

***RIPv2 uses the multicast address 224.0.0.9. Multicasting of routing messages is better than broadcasting because hosts and non-RIPv2 routers will ignore the multicast messages .

4: What is the purpose of the Route Tag field in the RIPv2 message?

*** When another routing protocol uses the RIPv2 domain as a transit domain, the protocol external to RIPv2 can use the Route Tag field to communicate information to its peers on the other side of the RIPv2 domain.

5: What is the purpose of the Next Hop field?

*** The Next Hop field is used to inform other routers of a next-hop address on the same multiaccess network that is metrically closer to the destination than the originating router.

6: What is the UDP port number used by RIPv2?

***RIPv2 uses the same UDP port number as RIPv1, port number 520.

7: Which one feature must a routing protocol have to be a classless routing protocol?

***A classless routing protocol does not consider the major network address in its route lookups, but just looks for the longest match.

8: Which one feature must a routing protocol have to use VLSM?

*** To support VLSM, a routing protocol must be able to include the subnet mask of each destination address in its updates.

9: Which two types of authentication are available with Cisco's RIPv2? Are they both defined in RFC 1723?

*** Cisco's implementation of RIPv2 supports clear-text authentication and MD5 authentication. Only clear-text authentication is defined in RFC 1723.

Routing Information Protocol

2006-10-31T16:48:00.000+05:30

1:What port does RIP use?

* RIP uses UDP port 520.

2:What metric does RIP use? How is the metric used to indicate an unreachable network?

* RIP uses a hop count metric. An unreachable network is indicated by setting the hop count to 16, which RIP interprets as an infinite distance.

3:What is the update period for RIP?

* RIP sends periodic updates every 30 seconds minus a small random variable to prevent the updates of neighboring routers from becoming synchronized.

4:How many updates must be missed before a route entry will be marked as unreachable?

* A route entry is marked as unreachable if six updates are missed.

5:What is the purpose of the garbage collection timer?

* The garbage collection timer, or flush timer, is set when a route is declared unreachable. When the timer expires, the route is flushed from the route table. This process allows an unreachable route to remain in the routing table long enough for neighbors to be notified of its status.

Kamal Hasan

2006-10-30T16:09:00.000+05:30

OSPF Q & A Part -II

2006-10-30T14:56:00.000+05:30

1: What are the five OSPF packet types? What is the purpose of each type?

*** The five OSPF packet types, and their purposes, are:

Hellos, which are used to discover neighbors, and to establish and maintain adjacencies

Updates, which are used to send LSAs between neighbors

Database Description packets, which a router uses to describe its link state database to a neighbor during database synchronization

Link State Requests, which a router uses to request one or more LSAs from a neighbor's link state database

Link State Acknowledgments, used to ensure reliable delivery of LSAs

2: What are LSA types 1 to 5 and LSA type 7? What is the purpose of each type?

*** The most common LSA types and their purposes are:

Type 1 (Router LSAs) are originated by every router and describe the originating router, the router's directly connected links and their states, and the router\xd5 s neighbors.

Type 2 (Network LSAs) are originated by Designated Routers on multiaccess links and describe the link and all attached neighbors.

Type 3 (Network Summary LSAs) are originated by Area Border Routers and describe inter-area destinations.

Type 4 LSAs (ASBR Summary LSAs) are originated by Area Border Routers to describe Autonomous System Boundary Routers outside the area.

Type 5 (AS External LSAs) are originated by Autonomous System Boundary Routers to describe destinations external to the OSPF domain.

Type 7 (NSSA External LSAs) are originated by Autonomous System Boundary Routers within not-so-stubby areas.

3: What are the four OSPF router types?

***The four OSPF router types are:

# Internal Routers, whose OSPF interfaces all belong to the same area

# Backbone Routers, which are Internal Routers in Area 0

# Area Border Routers, which have OSPF interfaces in more than one area

# Autonomous System Boundary Routers, which advertise external routes into the OSPF domain

4: What are the four OSPF path types?

***The four OSPF path types are:

Intra-area paths

Inter-area paths

Type 1 external paths

Type 2 external paths

5: What are the five OSPF network types?

*** The five OSPF network types are:

i)Point-to-point networks

ii) Broadcast networks

iii) Non-broadcast multi-access (NBMA) networks

iv) Point-to-multipoint networks

v) Virtual links

6: What is a Designated Router?

***A Designated Router is a router that represents a multiaccess network, and the routers connected to the network, to the rest of the OSFP domain.

7: How does a Cisco router calculate the outgoing cost of an interface?

***Cisco IOS calculates the outgoing cost of an interface as 108/BW, where BW is the configured bandwidth of the interface.

8: What is a partitioned area?

***An area is partitioned if one or more of its routers cannot send a packet to the area's other routers without sending the packet out of the area.

9: What is a virtual link?

*** A virtual link is a tunnel that extends an OSPF backbone connection through a non-backbone area.

10: What is the difference between a stub area, a totally stubby area, and a not-so-stubby area?

***A stub area is an area into which no type 5 LSAs are flooded. A totally stubby area is an area into which no type 3, 4, or 5 LSAs are flooded, with the exception of type 3 LSAs to advertise a default route. Not-so-stubby areas are areas through which external destinations are advertised into the OSPF domain, but into which no type 5 LSAs are sent by the ABR.

11: What is the difference between OSPF network entries and OSPF router entries?

*** OSPF network entries are entries in the route table, describing IP destinations. OSPF router entries are entries in a separate route table that record only routes to ABRs and ASBRs.

12: Why is type 2 authentication preferable over type 1 authentication?

***Type 2 authentication uses MD5 encryption, whereas type 1 authentication uses clear-text passwords.

13: Which three fields in the LSA header distinguish different LSAs? Which three fields in the LSA header distinguish different instances of the same LSA?

***The three fields in the LSA header that distinguish different LSAs are the Type, Advertising Router, and the Link State ID fields. The three fields in the LSA header that distinguish different instances of the same LSA are the Sequence Number, Age, and Checksum fields.

Important Networking Q & A

2006-10-28T15:20:00.000+05:30

1: What information must be stored in the route table?

** At a minimum, each entry of the routing table must include a destination address and the address of a next-hop router or an indication that the destination address is directly connected.

2: What does it mean when a route table says that an address is variably subnetted?

**Variably subnetted means that the router knows of more than one subnet mask for subnets of the same major IP address.

3: What are discontiguous subnets?

** Discontiguous subnets are two or more subnets of a major IP network address that are separated by a different major IP address.

4: What command is used to examine the route table in a Cisco router?

** show ip route is used to examine the routing table of a Cisco router.

5: What are the two bracketed numbers associated with the non-directly connected routes in the route table?

**The first bracketed number is the administrative distance of the routing protocol by which the route was learned. The second number is the metric of the route.

6: When static routes are configured to reference an exit interface instead of a next-hop address, in what way will the route table be different?

**When a static route is configured to reference an exit interface instead of a next-hop address, the destination address will be entered into the routing table as directly connected.

7: What is a summary route? In the context of static routing, how are summary routes useful?

**A summary route is a single route entry that points to multiple subnets or major IP addresses. In the context of static routes, summary routes can reduce the number of static routes that must be configured.

8: What is an administrative distance?

**An administrative distance is a rating of preference for a routing protocol or a static route. Every routing protocol and every static route has an administrative distance associated with it. When a router learns of a destination via more than one routing protocol or static route, it will use the route with the lowest administrative distance.

9: What is a floating static route?

** A floating static route is an alternative route to a destination. The administrative distance is set high enough that the floating static route is used only if a more-preferred route becomes unavailable.

10: What is the difference between equal-cost and unequal-cost load sharing?

**Equal-cost load sharing distributes traffic equally among multiple paths with equal metrics. Unequal-cost load sharing distributes packets among multiple paths with different metrics. The traffic will be distributed inversely proportional to the cost of the routes.

Universal Hero From V V

2006-10-26T19:14:00.000+05:30

Surya

2006-10-26T19:10:00.000+05:30

OSPF Q & A

2006-10-26T18:30:00.000+05:30

1: What is an OSPF neighbor?

*** From the perspective of an OSPF router, a neighbor is another OSPF router that is attached to one of the first router's directly connected links.

2: What is an OSPF adjacency?

***An OSPF adjacency is a conceptual link to a neighbor over which LSAs can be sent.

3: What is an LSA? How does an LSA differ from an OSPF Update packet?

***A router originates a link state advertisement to describe one or more destinations. An OSPF Update packet transports LSAs from one neighbor to another. Although LSAs are flooded throughout an area or OSPF domain, Update packets never leave a data link.

4: What is a link state database? What is link state database synchronization?

***The link state database is where a router stores all the OSPF LSAs it knows of, including its own. Database synchronization is the process of ensuring that all routers within an area have identical link state databases.

5: What is the default HelloInterval?

***The default OSPF HelloInterval is 10 seconds.

6: What is the default RouterDeadInterval?

***The default RouterDeadInterval is four times the HelloInterval.

7: What is a Router ID? How is a Router ID determined?

***A Router ID is an address by which an OSPF router identifies itself. It is either the numerically highest IP address of all the router's loopback interfaces, or if no loopback interfaces are configured, it is the numerically highest IP address of all the router's LAN interfaces.

8: What is an area?

***An area is an OSPF sub-domain, within which all routers have an identical link state database.

9: What is the significance of area 0?

***Area 0 is the backbone area. All other areas must send their inter-area traffic through the backbone.

10: What is MaxAge?

***MaxAge, 1 hour, is the age at which an LSA is considered to be obsolete.

Cute Baby Take Bath

2006-10-26T17:57:00.000+05:30

Aish Collection's

2006-09-28T10:54:00.000+05:30

Aish Photo's

2006-09-25T10:37:00.000+05:30

Aish pictures

2006-09-23T16:02:00.000+05:30

Surya's Wedding Photo's

2006-09-21T13:03:00.000+05:30

Surya's Wedding Photo's

2006-09-20T15:06:00.000+05:30

Surya's Wedding Photo's

2006-09-20T14:44:00.000+05:30