What happens when a BGP router receives a route with an unreachable next hop?

What happens when a BGP router receives a route with an unreachable next hop?

• A. It sends an error message to the originating router.
• B. It discards the route and does not add it to the routing table.
• C. It adds the route but does not prefer it for final selection.
• D. It accepts the route for potential future use.

Answer: (C)

When a BGP router receives a route with an unreachable next hop, it processes the route information according to specific BGP rules. The correct option states that the router adds the route but does not prefer it for final selection. The reason this is the correct answer lies in the behavior of BGP in relation to routing policies and the management of routes. When a BGP router learns about a new route, it will store the route in its routing information base (RIB), regardless of the reachability of the next hop. This is because the router might receive updates about the next hop's status later, or there may be policies that involve future considerations for that route. However, since the next hop is currently unreachable, the BGP router will not use this route for outbound traffic in its decision-making process when selecting the best route for a particular destination. In contrast, an unreachable next hop route will not be advertised to other routers, and it won’t be part of the active forwarding decisions until the next hop becomes reachable. This strategic approach allows BGP to maintain a robust routing structure and adapt to changes in the network topology without immediately discarding potentially useful route information. The other choices reflect actions that BGP does not take in these scenarios. For

When a BGP router receives a route with an unreachable next hop, it processes the route information according to specific BGP rules. The correct option states that the router adds the route but does not prefer it for final selection.

The reason this is the correct answer lies in the behavior of BGP in relation to routing policies and the management of routes. When a BGP router learns about a new route, it will store the route in its routing information base (RIB), regardless of the reachability of the next hop. This is because the router might receive updates about the next hop's status later, or there may be policies that involve future considerations for that route. However, since the next hop is currently unreachable, the BGP router will not use this route for outbound traffic in its decision-making process when selecting the best route for a particular destination.

In contrast, an unreachable next hop route will not be advertised to other routers, and it won’t be part of the active forwarding decisions until the next hop becomes reachable. This strategic approach allows BGP to maintain a robust routing structure and adapt to changes in the network topology without immediately discarding potentially useful route information.

The other choices reflect actions that BGP does not take in these scenarios. For