What is the main purpose of the Split Horizon rule in routing?

The main purpose of the Split Horizon rule in routing is to prevent routing loops. This mechanism is a vital aspect of distance-vector routing protocols, where routers share routing information with their neighboring routers. When the Split Horizon rule is applied, a router will not advertise a route back out the same interface from which it learned that route. This effectively prevents the possibility of a routing loop—where packets get caught in a cycle and continuously circulate without being delivered to their destination. By implementing this rule, the network maintains more stable and efficient routing tables, minimizing erroneous routing information that could lead to loops and unnecessary traffic. This foundational principle enhances overall network reliability by ensuring that routes are only communicated through appropriate paths, contributing to sustained operational integrity.