Introduction
Dynamic routing protocols exchange routing information before populating routing tables and forwarding packets. For this task, RIP (routing information protocol) put into play many machanisms and rules to guarantee that this routing information exchange is consistent: not contradictory among routers. An example of such inconsistency is to receive the same routing information on two different router interface… the router is unable to resolve the next hop for traffic matching this route to only one interface!
Split-horizon to prevent routing loops
One of those mechanism that RIP put into play is Split-Horizon rule. Per the split-horizon rule, RIP routers don’t send an update back on the interface it was received on. We’re talking about routing information and not the data packet itself.
What is the challenge here? In addition to enhancing bandwidth usage and system resources consumption, Split horizon helps prevent routing loops… let’s focus on how split-horizon helps prevent routing loops;
In this kind of loop the routing information is lost, incoherent between the domain routers. The routers are unable to encode the next hop for received packets (matching this route) due to routing table information frequent changes, lack or errors. The problem is even more impacting if other features depend on route lookup… because of the lack of this information, CPU is engaged to handle packets in an exception mode which may complicate things even more.
