Ondrej Zajicek <santiago@crfreenet.org> writes:
On Wed, Jan 27, 2021 at 03:23:25PM +0000, 0.bgp@elloe.vision wrote:
We are setting up a container based proof of concept with IPv6 only using ECMP, ANYCAST, BGP with BFP and Bird2 and I've hit a problem where BFD doesn't recover after a local link goes down and comes back and are seeking some advice as whether this is expected behaviour or a bug.
Based on quick evaluation, seems to me that it is a combination of race condition in BIRD and systemd-networkd behavior. There is a condition in BIRD that when a BFD session is added during the time IP address on that link is added/removed, sometimes it fails to add the socket.
We see this as well. It seems to only affect IPv6. We have the additional complication that the router ends up learning the linknet address via OSPF on another path, which prevents BFD from ever recovering. We worked around it with check scripts which look for linknet addresses that aren't in the routing table and add them, but it's ugly and still causes outages. -- Alasdair Muckart Network Engineer Catalyst IT - Expert Open Source Solutions Mobile: +64 22 638 5141 | DDI: +64 4 897 7794 | www.catalyst.net.nz