Poison Reverse vs Split Horizon

Routing protocols determine optimal paths for data transmission through networks by maintaining and updating routing tables. Two important loop-prevention techniques used in distance-vector routing protocols like RIP and EIGRP are Poison Reverse and Split Horizon.

Both techniques address the counting-to-infinity problem that occurs when routers continuously exchange routing information, potentially creating loops that cause packets to circulate indefinitely.

Split Horizon

Split Horizon is a simple rule that prevents a router from advertising a route back through the same interface from which it learned that route. This technique stops routing information from bouncing between routers.

Poison Reverse

Poison Reverse actively advertises unreachable routes with an infinite metric (typically 16 hops in RIP) back to the source. Instead of suppressing the route announcement, it explicitly marks the route as unreachable.

Key Differences

Common Applications

Both techniques are primarily used in RIP and EIGRP implementations. Split Horizon is suitable for bandwidth-constrained environments, while Poison Reverse is preferred when faster convergence is critical, such as in financial networks or real-time communication systems.

Conclusion

Split Horizon and Poison Reverse are essential loop-prevention mechanisms in distance-vector routing protocols. Split Horizon reduces network traffic by suppressing route advertisements, while Poison Reverse ensures faster convergence by explicitly invalidating failed routes.