BGP Features for Successful Route Exchanges | Cisco Exam 300-420-ENSLD

BGP Features for Successful Route Exchanges

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Which two BGP features will result in successful route exchanges between eBGP neighbors sharing the same AS number? (Choose two.)

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A. B. C. D. E.

DE.

BGP (Border Gateway Protocol) is a protocol used to exchange routing information between different Autonomous Systems (AS) in the Internet. When eBGP neighbors are part of the same AS number, it is necessary to configure specific BGP features to allow for successful route exchanges.

The two BGP features that will result in successful route exchanges between eBGP neighbors sharing the same AS number are:

  1. allow-as-in: This feature allows BGP to accept routes that have the same AS number as the local AS number. When a router receives an update from an eBGP neighbor that has the same AS number, it normally discards the route because it assumes that it is a loop. However, by enabling allow-as-in, the router will accept the route and advertise it to its other neighbors.

  2. as-override: This feature is used to modify the AS path information in updates received from eBGP neighbors that have the same AS number. When a router receives an update from such a neighbor, it normally appends its own AS number to the AS path information before advertising it to its other neighbors. However, by enabling as-override, the router will replace the AS number of the eBGP neighbor with its own AS number before advertising the route. This allows the route to be advertised to other ASes without causing loops.

The other options are:

A. advertise-best-external: This feature allows a router to advertise the best external route to its eBGP neighbors. It is used when a router has multiple paths to the same destination and wants to advertise the best one to its neighbors.

B. bestpath as-path ignore: This feature causes the router to ignore the AS path information when selecting the best path to a destination. It is used when the AS path information is not important or when there are multiple paths with the same AS path information.

C. client-to-client reflection: This feature is used in a route reflector setup to allow clients to exchange routes directly with each other, without going through the route reflector.

Therefore, options A, B, and C are not relevant to the scenario described in the question.

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