Which of the following is a common method for preventing routing loops?

• A. Route Poisoning
• B. Triggered Updates
• C. Split Horizon
• D. Hold-Down Timers

Answer: (C)

Preventing routing loops comes down to stopping new route information from circulating in ways that create contradictory paths. Split Horizon does exactly this in distance‑vector routing: a router does not advertise a route back out the same interface from which it learned it. By keeping information from going back toward the neighbor that shared it, the path that could loop between routers is prevented from forming. In some setups this is paired with poison reverse, where the route is advertised back with an infinite metric to make sure the neighbor doesn’t use it, but the key idea remains preventing that back‑and‑forth advertisement that seeds loops.

Other techniques help with convergence and stability but don’t specifically stop a route from being reflected onto the same interface. Route poisoning marks a failed route as unreachable to hasten convergence, hold‑down timers delay changes to avoid flapping, and triggered updates push changes quickly to speed up consistency—yet the primary loop‑prevention mechanism in many protocols is split horizon.