Follow up question on "next hop self"

[Alarig Le Lay]

Hi,

On ven. 20 déc. 22:36:29 2019, Nico Schottelius wrote:
> 
> Hello,
> 
> I was wondering about how bird solves the following problem with next
> hop self enabled:
> 
> R1 <-------->  R2
>  \             /
>   \           /
>    upstream 1
> 
> So both routers receive the same routes from upstream and insert them
> with the same local_pref. With "next hop self" on, both routers will
> think that the path is not the same and potentially either of the two
> routers could start routing via the other router instead of via upstream
> directly.
> 
> What is the typical approach to solve this situation correctly?
> Does making setting the local_pref lower if received from an
> iBGP router make sense in that case?
> 
> Best regards,
> 
> Nico

There will be no loop because eBGP paths are preferred over iBGP ones if
the routes are equals. https://tools.ietf.org/html/rfc1771#section-9.1

BTW, using classical iBGP, RRs and an IGP will solve many of this kind
of problems.

-- 
Alarig