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I was solving an assignment on routing protocols and the following question came up. I am unable to come up with the solution. Please help.

A network of 4 routers A, B, C and D is arranged like this: 

A_____B_____C_____D
   3     2     1

The routers use the distance vector routing, using the number of hops as the metric. The value “8” is used by all routers to indicate “infinity” (to conclude that a router is unreachable).

The link C-D goes down.

a. How many exchanges would it require for each of them to conclude that D is unreachable? At each exchange, show the distances all the routers maintain to router D.

b. Assume that the routers follow split horizon. How many exchanges are needed for the routers to conclude that D is unreachable? At each exchange, show the distances all the routers maintain to router D.

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1 Answers1

1

Solution

I wrote it by hand, hope it is legible. This solution is for part (a).

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