3. Distance-vector routing: Count-to-infinity problem and poisoned reverse (10 points) Consider the folllowing network topology. Suppose that to tackle the count-to- infinity problem, the following poisoned reverse rule is used in the distance vector routing algorithm: If Z routes through Y to get to X then Z tells Y its (Z's) distance to X is infinite. 14 2 a) (3 pts) When the distance-vector routing is stablized, router B, C, D will inform their distances to A to each other. What distance values do B, C, D inform their neighbors of their distances to A? (7 pts) If the link cost from A to B has changed from 2 to 30, please show how the routing tables in B, C, D are updated. Specifically, show how the routing entries in B, C, and D to distance A are updated over time. How many iterations are needed for the distance-vector routing to reach a stable state again? b)