In a BGP test scenario, when a router fails, what do the remaining routers communicate to maintain routing?

• A. It bypasses the affected router to maintain routing
• B. It restarts the affected router
• C. It signals the attack origin
• D. It floods the network with more updates

Answer: (A)

In BGP, routers keep traffic flowing by quickly adapting to changes in reachability. When a router fails, neighboring routers detect that routes through that device are no longer valid and shift to alternative paths learned from other peers, effectively bypassing the failed router to maintain routing. They withdraw the unavailable routes and advertise the remaining viable paths, allowing the network to converge on a new, stable set of routes. The other options don’t fit because restarting the failed router is not something the remaining routers do; signaling the attack origin isn’t part of how routing tables are maintained; and flooding the network with more updates would cause instability rather than maintain reliable routing.