Comment 9 for bug 2017888

https://review.opendev.org/c/openstack/networking-bgpvpn/+/883060

I've published a WIP change in Gerrit that contains our modifications.
It's still not finished yet as I have to do more testing and maybe adding some additional unit tests, but it should work fine already.

Regarding the AS numbers:

To my understanding networking-bgpvpn does not allow to specify an AS number for a specific BGPVPN.
Right now that value is loaded from a config in networking-bgpvpn, so up to my understanding its the same for the whole region where this instance of neutron-server is used.
Ignoring that value and using something configured on the agents would at least make this significant for only the node where the agent runs.
I think that's also what happens today, the locally configured AS is used for configuring the config snippets into FRR.
As each VNI is usually announced through the same EVPN sessions in the underlay that makes the most sense.

The only useful scenario I could imagine would be a feature where we would offer regular BGP sessions to external routers so that a given customer could connect their external networks to their cloud environment. These routes would then be installed as type 5 routes into the customers L3 VNI. But thats a different topic and to my understanding not in scope for ovn-bgp-agent and for networking-bgpvpn as well.

As to my understanding the AS number is not used and there is no usecase to define that centrally I have removed that field in the change mentioned above.