Resolve a BGP next-hop with another BGP route

[mikma.bird at lists.m7n.se]

On 30 September 2019 01:52:22 CEST, Ondrej Zajicek

>Yes. Technically it is not because the other route is also BGP, but
>because the other route is also recursive / also has indirect next hop.
>BIRD implements only one level of indirection.
>
>Is this a problem? Which use cases require more levels of indirections?

"The BGP Tunnel Encapsulation Attribute" is one example:

> 7. Recursive Next Hop Resolution > Suppose that:
> 
>    o  a given packet P must be forwarded by router R1;
> 
>    o  the path along which P is to be forwarded is determined by BGP
>       UPDATE U1;
> 
>    o  UPDATE U1 does not have a Tunnel Encapsulation attribute;
> 
>    o  the next hop of UPDATE U1 is router R2;
> 
>    o  the best path to router R2 is a BGP route that was advertised in
>       UPDATE U2;
> 
>    o  UPDATE U2 has a Tunnel Encapsulation attribute.
> 
>    Then packet P MUST be sent through one of the tunnels identified in
>    the Tunnel Encapsulation attribute of UPDATE U2.  See Section 5 for
>    further details.


https://tools.ietf.org/html/draft-ietf-idr-tunnel-encaps-13#section-7

/Mikma