On Thu, 1 Dec 2022 08:55:02 +0100
Claudio Jeker wrote:
> On Thu, Dec 01, 2022 at 01:01:16AM +0200, Gregory Edigarov wrote:
> > Hello,
> >
> > Having two sites in different physical locations, siteA is connected
> > via uplink1 and uplink2, siteB is connected via uplink3 and uplink4.
> > I want to announce prefixes from siteB if ASn not found originating
> > from siteA, and vice versa. I.e. a feature that will work alike
> > 'enforce localas yes' but start announces when ASn is gone. I could
> > done it with some scripting, but would prefer to have it in bgpd.
> > Is this possible solely with OpenBGPD?
>
> Run an ibgp session between siteA and siteB. Announce only your
> prefixes on those sessions. Tag them with a community. Make sure that
> these prefixes are more preferred than the one you put in as backup.
> Filter out prefixes with the tag. More or less like this:
>
> # backup route using low localpref to be less preferred
> network 192.0.2.0/24 set { localpref 1 }
>
> # send my networks to siteA tagged with community
> deny to siteA
> allow to siteA prefix-set mynetworks set community local-as:42
> # filter out announcement originated from siteA
> deny to any community local-as:42
>
Many thanks for the idea, Claudio.
The solution is working like a charm.
