Q3:Explain link state routing vs distance vector routing.

A:

See Fig. 1-1 below. If all routers were running a Distance Vector protocol, the path or 'route' - See more at: http://www.inetdaemon.com/tutorials/internet/ip/routing/dv_vs_ls.shtml#sthash.pMwGkpMj.dpuf

See Fig. 1-1 below. If all routers were running a Distance Vector protocol, the path or 'route' chosen would be from A  B directly over the ISDN serial link, even though that link is about 10 times slower than the indirect route from A  C  D  B.
A Link State protocol would choose the A  C  D  B path because it's using a faster medium (100 Mb ethernet). In this example, it would be better to run a Link State routing protocol, but if all the links in the network are the same speed, then a Distance Vector protocol is better.
- See more at: http://www.inetdaemon.com/tutorials/internet/ip/routing/dv_vs_ls.shtml#sthash.pMwGkpMj.dpuf

See Fig. 1-1 below. If all routers were running a Distance Vector protocol, the path or 'route' chosen would be from A  B directly over the ISDN serial link, even though that link is about 10 times slower than the indirect route from A  C  D  B.
A Link State protocol would choose the A  C  D  B path because it's using a faster medium (100 Mb ethernet). In this example, it would be better to run a Link State routing protocol, but if all the links in the network are the same speed, then a Distance Vector protocol is better.
- See more at: http://www.inetdaemon.com/tutorials/internet/ip/routing/dv_vs_ls.shtml#sthash.pMwGkpMj.dpuf

See Fig. 1-1 below. If all routers were running a Distance Vector protocol, the path or 'route' chosen would be from A  B directly over the ISDN serial link, even though that link is about 10 times slower than the indirect route from A  C  D  B.

A Link State protocol would choose the A  C  D  B path because it's using a faster medium (100 Mb ethernet). In this example, it would be better to run a Link State routing protocol, but if all the links in the network are the same speed, then a Distance Vector protocol is better.

- See more at: http://www.inetdaemon.com/tutorials/internet/ip/routing/dv_vs_ls.shtml#sthash.pMwGkpMj.dpuf

ee Fig. 1-1 below. If all routers were running a Distance Vector protocol, the path or 'route' chosen would be from A  B directly over the ISDN serial link, even though that link is about 10 times slower than the indirect route from A  C  D  B.
A Link State protocol would choose the A  C  D  B path because it's using a faster medium (100 Mb ethernet). In this example, it would be better to run a Link State routing protocol, but if all the links in the network are the same speed, then a Distance Vector protocol is better.

FIG. 1-1 - See more at: http://www.inetdaemon.com/tutorials/internet/ip/routing/dv_vs_ls.shtml#sthash.pMwGkpMj.dpuf

ee Fig. 1-1 below. If all routers were running a Distance Vector protocol, the path or 'route' chosen would be from A  B directly over the ISDN serial link, even though that link is about 10 times slower than the indirect route from A  C  D  B.
A Link State protocol would choose the A  C  D  B path because it's using a faster medium (100 Mb ethernet). In this example, it would be better to run a Link State routing protocol, but if all the links in the network are the same speed, then a Distance Vector protocol is better.

FIG. 1-1 - See more at: http://www.inetdaemon.com/tutorials/internet/ip/routing/dv_vs_ls.shtml#sthash.pMwGkpMj.dpuf

See Fig. 1-1 below. If all routers were running a Distance Vector protocol, the path or 'route' chosen would be from A  B directly over the ISDN serial link, even though that link is about 10 times slower than the indirect route from A  C  D  B.
A Link State protocol would choose the A  C  D  B path because it's using a faster medium (100 Mb ethernet). In this example, it would be better to run a Link State routing protocol, but if all the links in the network are the same speed, then a Distance Vector protocol is better.

FIG. 1-1
- See more at: http://www.inetdaemon.com/tutorials/internet/ip/routing/dv_vs_ls.shtml#sthash.pMwGkpMj.dpuf

See Fig. 1-1 below. If all routers were running a Distance Vector protocol, the path or 'route' chosen would be from A  B directly over the ISDN serial link, even though that link is about 10 times slower than the indirect route from A  C  D  B.
A Link State protocol would choose the A  C  D  B path because it's using a faster medium (100 Mb ethernet). In this example, it would be better to run a Link State routing protocol, but if all the links in the network are the same speed, then a Distance Vector protocol is better.

FIG. 1-1
- See more at: http://www.inetdaemon.com/tutorials/internet/ip/routing/dv_vs_ls.shtml#sthash.pMwGkpMj.dpuf

Q1: Explain Split Horizon with poison reversed.

A:
Split horizon is a method of preventing a routing loop in a network. The basic principle is simple: Information about the routing for a particular packet is never sent back in the direction from which it was received.

Split horizon can be achieved by means of a technique called poison reverse. This is the equivalent of route poisoning all possible reverse paths - that is, informing all routers that the path back to the originating node for a particular packet has an infinite metric. Split horizon with poison reverse is more effective than simple split horizon in networks with multiple routing paths, although it affords no improvement over simple split horizon in networks with only one routing path.

RIP for IP, like most distance vector routing protocols, announces its routes in an unsynchronized and unacknowledged manner. This can lead to convergence problems. However, you can enable modifications to the announcement algorithms to reduce convergence time in most situations.

Count-to-Infinity Problem
The classic distance vector convergence problem is known as the count-to-infinity problem and is a direct result of the asynchronous announcement scheme. When RIP for IP routers add routes to their routing table, based on routes advertised by other routers, they keep only the best route in the routing table and they update a lower cost route with a higher cost route only if is being announced by the same source as the current lower cost route. In certain situations, as illustrated in Figures 3.1 through 3.5, this causes the count-to-infinity problem.

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