Bird redundant routers with same AS on same location and prefix delegation to lower router

[Ondrej Zajicek]

On Mon, Sep 18, 2017 at 03:44:40PM +0300, Andrew wrote:
> Hi.
> 
> Something like:
> 
> template bgp bgp_local {
>         local as my_as;
>         import filter import_bgp;
>         export filter export_bgp;
> multihop;
>         rr client;
>         rr cluster id 1.0.0.1;
> }
> 
> # R2 - also RR; import all routes from it
> protocol bgp bgp_peer_r2 from bgp_local {
>         description "R2";
>         neighbor x.x.x.x as my_as;
>         import all;
> }
> 
> # C1 - client
> protocol bgp bgp_peer_c1 from bgp_local {
>         description "C1";
>         neighbor x.x.x.y as my_as;
> }
> 
> cluster id should be same on all RRs.

Hi

Note that you configured your RR-RR session as mutual-RR-client. While
such setting has also its uses, the usual way is to configure RR-RR
session as regular IBGP session (without 'rr client'). But both
approaches will work, and unless you have more non-RR-clients it does not
matter.

Another approach is to set each RR as independent RR cluster (with own
RR cluster ID) and just connect RR clients to two RR clusters. Such
approach is less customary, but has some advantages.

To the original question - loops between RRs are prevented by
CLUSTER_LIST option, so there is no reason to be afraid.

If there are just two dedicated RRs in one cluster (which is not the
case in the original example as they also have EBGP links), you can just
skip RR-RR session altogether as CLUSTER_LIST prevents to propagate
anything by that session.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."