After receiving a BGP route, which two conditions are verified by the receiving router to ensure that the received route is valid? (Choose two)

Question

Options

• AThe AS-path length is greater than 0.
• BThe loops do not exist.
• CThe next hop is reachable.
• DThe local preference is greater than 0.

• A
  7% (3)
• B
  84% (38)
• D
  9% (4)

Explanation

B is correct because the loops do not exist is one of the conditions that are verified by the receiving router to ensure that the received BGP route is valid. A loop in BGP means that a route has been advertised by the same AS more than once, which can cause routing instability and inefficiency. To prevent loops, BGP uses the AS-path attribute, which lists the AS numbers that a route has traversed from the origin to the destination. The receiving router checks the AS-path attribute of the received route and discards it if it finds its own AS number in the list. This way, BGP avoids accepting routes that contain loops. C is correct because the next hop is reachable is one of the conditions that are verified by the receiving router to ensure that the received BGP route is valid. The next hop is the IP address of the next router that is used to forward packets to the destination network. The receiving router checks the next hop attribute of the received route and verifies that it has a valid route to reach it. If the next hop is not reachable, the received route is not usable and is rejected by the receiving router. This way, BGP ensures that only feasible routes are accepted.

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