How would you troubleshoot a distance-vector routing issue where routes are stuck in a hold-down state?

• A. Rebooting all routers to reset the routing table.
• B. Verify neighbor adjacency, timers, route poisoning, hold-down settings, AD values, and ensure updates propagate; check for misconfigurations or discontiguities.
• C. Disable all hold-down timers to allow quick changes.
• D. Manually setting all routes to the next-hop directly.

Answer: (B)

Hold-down behavior in distance-vector routing prevents rapid changes to a route after it’s determined unreachable, which can keep a route stuck in hold-down even when a valid path exists. To troubleshoot, you want to inspect the factors that control how and when routes are announced and accepted: are neighboring routers forming and keeping adjacency, are the routing timers (update, invalid, hold-down, and flush) configured consistently, is route poisoning being used to signal an unreachable metric, are hold-down settings appropriate for the network, and are the administrative distance values and update propagation correct. Also check for any misconfigurations or network discontiguities that could stop timely updates from propagating. When these elements are aligned, the network can converge properly and routes leave hold-down as expected.

Rebooting all routers isn’t targeting the root cause and can introduce downtime without guaranteeing the hold-down issue is resolved. Disabling hold-down timers outright can lead to routing instability and loops. Manually setting all routes to the next-hop bypasses the dynamic protocol entirely and isn’t a scalable or accurate solution to a hold-down problem.