Cisco Certified Network Associate (CCNA) Practice Exam

What does split horizon prevent in EIGRP?

1. Routers from sending updates to all neighbors

2. Routers from receiving back their own updates

3. Bridges from creating loops

4. Static routes from being advertised

The correct answer is: Routers from receiving back their own updates

The correct answer is that split horizon prevents routers from receiving back their own updates in Enhanced Interior Gateway Routing Protocol (EIGRP). This technique helps to reduce routing loops by ensuring that information about routes learned from one interface is not sent back out of the same interface. When a router learns information about a route through one of its interfaces, it is prevented from advertising that route back through the same interface. This is vital in maintaining route stability and efficiency in the network. It minimizes the chances of redundant route information circulating back to the originating router, which could potentially cause confusion or unnecessary updates. Other choices do not accurately describe the function of split horizon. For instance, preventing routers from sending updates to all neighbors would be more related to the use of route summarization or designated routing methods. Preventing bridges from creating loops pertains to Spanning Tree Protocol concepts, not EIGRP. Lastly, the option on static routes being advertised does not apply, as split horizon addresses dynamic routing updates rather than static routing behaviors.