Understanding BGP Auto-discovered Neighbor

SUMMARY Use BGP auto-discovered neighbor to configure BGP peering by interface rather than by specifying remote or local neighbor IP addresses.

To establish a BGP session between routers, you must explicitly configure BGP groups and peers by address. BGP peering sessions require that you identify source and destination IP addresses for endpoints of the TCP communication. Therefore, explicitly configuring these addresses is an obstacle to network scale-out and an opportunity for misconfiguration.

To streamline your BGP configuration, we have removed the need to configure per-peer address from BGP. Use BGP auto-discovered neighbor to configure BGP peering by interface rather than by specifying remote or local neighbor IP addresses. This includes use of implicit or protocol mechanisms to discover the IP addresses for use in the TCP peering sessions.

Note:

Peering behavior and address usage must be explicitly configured to avoid peering changes based on interface address changes due to configuration or address validity (for example, IPv6 Duplicate Address Detection (DAD)).

BGP determines the address families to peer over based on the configuration. The peering sessions come up based on availability of the interface addresses for the determined families. The peer link-local address is discovered using IPv6 neighbor discovery (RFC4861) and creates a BGP session toward that neighbor. A link-local address is generated even when IPv6 interfaces have no addresses configured.

Note:

You must enable IPv6 neighbor discovery for this feature to work.