300-410 Question 18
Single answerA network engineer is troubleshooting a routing loop issue in a small enterprise network. The network uses EIGRP as its routing protocol and has multiple paths configured between routers. During the investigation, the engineer notices that a loop is forming when a router advertises a route back to the originating router. Which loop prevention mechanism should the engineer implement to resolve this issue?
- A
Enable split horizon on the affected interfaces.
- B
Configure route tagging to filter the looped routes.
- C
Enable route poisoning to mark the routes as unreachable.
- D
Adjust the EIGRP metric to prioritize alternative paths.
Show answer and explanation
Correct answer: A
Explanation
Split horizon is a loop prevention mechanism that stops a router from advertising a route back out through the same interface it was learned on, which is the root cause of the issue described. This mechanism is explicitly designed to handle routing loops in protocols like EIGRP and RIP.
- A. Correct.
Split horizon prevents a route from being advertised back out of the interface from which it was learned, effectively preventing routing loops.
- B. Incorrect.
Route tagging is used for filtering or identification purposes but does not inherently prevent loops in this scenario.
- C. Incorrect.
Route poisoning is used to mark routes as unreachable, but it is more commonly used in distance-vector protocols like RIP, not as a primary solution for this EIGRP-specific loop issue.
- D. Incorrect.
Adjusting the EIGRP metric might influence path selection but does not directly address the root cause of the routing loop.