How will a BGP router process a route with an unreachable next hop?

How will a BGP router process a route with an unreachable next hop?

• A. It sends an error message to the router that sends the Update message
• B. It does not add this route to its BGP routing table and discards this route
• C. It accepts and adds this route to its BGP routing table, but it will not be preferred
• D. It accepts and adds this route to its BGP routing table, making it eligible for selection

Answer: (C)

In Border Gateway Protocol (BGP), the handling of routes with unreachable next hops is critical for ensuring the stability and integrity of the routing process. When a BGP router processes an update message that contains a route with an unreachable next hop, it indeed accepts this route and adds it to its BGP routing table. However, it is important to note that just because a route is added to the routing table doesn't mean it will be preferred for use in forwarding traffic. The router does not immediately discard a route with an unreachable next hop; instead, it can still maintain it in the table for potential future reference. Such routes would not be chosen for actual routing decisions unless the next hop becomes reachable again. This behavior allows the router to maintain a complete view of all known routes, along with their associated next-hop reachability status, and might be useful for network administrators for troubleshooting or planning purposes. The other options highlight behaviors that do not align with the established functionality of BGP routers; BGP does not discard routes solely based on next-hop reachability, nor does it send error messages in response solely to an unreachable next hop without further implications or context. The acceptance and storage of such routes offer a more flexible and robust routing protocol that can adapt to changing

In Border Gateway Protocol (BGP), the handling of routes with unreachable next hops is critical for ensuring the stability and integrity of the routing process. When a BGP router processes an update message that contains a route with an unreachable next hop, it indeed accepts this route and adds it to its BGP routing table. However, it is important to note that just because a route is added to the routing table doesn't mean it will be preferred for use in forwarding traffic.

The router does not immediately discard a route with an unreachable next hop; instead, it can still maintain it in the table for potential future reference. Such routes would not be chosen for actual routing decisions unless the next hop becomes reachable again. This behavior allows the router to maintain a complete view of all known routes, along with their associated next-hop reachability status, and might be useful for network administrators for troubleshooting or planning purposes.

The other options highlight behaviors that do not align with the established functionality of BGP routers; BGP does not discard routes solely based on next-hop reachability, nor does it send error messages in response solely to an unreachable next hop without further implications or context. The acceptance and storage of such routes offer a more flexible and robust routing protocol that can adapt to changing