Homework sheet for Bellman Ford - Distance Vector Routing Algorithm

Question

If the longest loop free path in the network is N, then the Bellman Ford routing algorithm will converge to the lowest cost spanning tree after N iterations.
This is true, but
What happen if they converge before N iterations?

Answer 1

If the algorithm converges early, then it will simply continue to run (each node sharing its distance vector values with its neighbors), but none of the distance values will change.

The point is that after N rounds, everyone WILL know the shortest distances to each other nodes (assuming that no links/nodes are changing).

Answer 2

The iterations will continue to run, but the lowest cost value will be same after it has reached the lowest value. After N (longest loop free path) iterations we can be sure that we have achieved the lowest costs for each.