On any internetwork, it is possible that more than one path to a destination may exist, with the same distance. For example, consider the figure below. This network consists of three networks. From Router A, network 172.16.0.0 can be reached in two possible ways – both via Router B and Router C. In both cases, the hop count to network 172.16.0.0 is identical – 1 hop. A distance vector protocol like RIP decides which route to take based on hop count, but can also load-balance over routes with the same hop-count in a round-robin fashion. In this case, some packets will be sent to network 172.16.0.0 via Router B, and some via Router C. It’s worth remembering, however, that hop count is the only metric used by RIP. For example, the link between A and C is only 64kbps, while the link between A and B is a T3 line. Even though AB is a much faster link than AC, Router A still sees both paths as equal. Such is how RIP sees the world.
Figure: Network 172.16.0.0 is available to Router A via two paths, both with a hop count of 1.
