This is working again in VyOS 1.2.3 GA. I have tested both the simple configuration mentioned above and my actual configuration with a bunch of BGP peers. Thank you very much!

@hagbard I don't know if this is somehow relevant regarding VyOS 1.3, but i have tested it with VyOS 1.2.3-epa1 just today and it works perfectly.

I'm sorry to bother with this issue again, but as I need to upgrade some VyOS 1.2.x routers in the near future, I would be grateful for any information on how to do this the best way regarding the changes stated above. As I have already mentioned, older nightlies don't set "native_ipv6" in the keepalived.conf. So if I upgrade one device at a time, VRRP will be broken until I have also upgraded the other devices. Do you have any advice how I should deal with this problem? Upgrading all devices at the same time is not really an option with my setup, but maybe there is some kind of reasonable workaround which you would recommend?

While that is true, older nightly versions don't set "native_ipv6" in the keepalived.conf, so any back-to-back updates will result in broken VRRP configurations. In addition, it is my understanding that you can't use both IPv4 and IPv6 in one VRRP group in newer versions of keepalived or rather you should not do it. Therefore simply adding "native_ipv6" may not be the best way to implement IPv6 support.

This can also be a problem for people using 1.2.x, as the "native_ipv6" line has also made it's way into vyatta-keepalived.pl in those nightly versions at some point in the past. So trying to upgrade from some early 2017 nightly to a current version may break VRRP in 1.2.x too, at least if you are not upgrading all devices at the same time.

This patch should also be included in 1.2.x, as i have seem similar behaviour with nightly builds.