Does the BGP router-id need to be reachable?

[Julian Ortiz]

Hi experts,

It was long time ago when I studied BGP, and these days I was doing a lab and got some issues related with the BGP router-id. I found this post:

https://community.cisco.com/t5/routing/bgp-router-id-and-loopback/td-p/1611333

Herve says "The router-id must not even need to be an existing ip address of the router (as long as it remains a unique identifier of course) and must not need to be network-reachable."

If the router-id is not an existing IP address or reachable, how can the neighbors reach that BGP router for sending BGP updates to it?

Regards,

Julián

[Richard Burts · Accepted solution]

Julián

In configuring BGP you configure a neighbor using a neighbor address. BGP uses the neighbor address to send updates and does not use router id to send updates. The neighbor address must be reachable but router id does not.

[Julian Ortiz]

Hi Richard,

Many thanks for the clarification, now it is clear

Regards,

Julián

[Richard Burts]

Julián

You are welcome. I am glad that my explanation was helpful. Thank you for marking this question as solved. This will help other participants in the community to identify discussions which have helpful information. This community is an excellent place to ask questions and to learn about networking. I hope to see you continue to be active in the community.