External BGP Session

C

In an external BGP (eBGP) session, the BGP neighbors belong to a different autonomous system (AS). Therefore, option B is the correct answer.

An autonomous system is a network or a group of networks under a common administrative domain that uses a single routing policy. BGP is used to exchange routing information between different ASes. In an eBGP session, BGP is used to exchange routing information between routers in different ASes.

BGP sessions can be established using any interface that is reachable from the remote BGP neighbor. However, it is recommended to use loopback interface addresses for BGP peering, as loopback interfaces are always up and provide better stability and flexibility. Therefore, option D is not entirely correct.

BGP sessions do not rely on a static route for reachability. Instead, BGP uses TCP connections to establish a connection between the BGP peers. Once the TCP connection is established, BGP can exchange routing information with the remote peer. Therefore, option C is incorrect.

In summary, an eBGP session is established between BGP neighbors belonging to different ASes, and it is recommended to use loopback interface addresses for BGP peering. BGP sessions do not rely on a static route for reachability, but instead use TCP connections to establish a connection between the BGP peers.