It looks like that IPv6 only BGP peering sessions over a peer group are not supported. The following configuration applies with an error
```must set remote-as or peer-group with remote-as defined```
but the configuration is then present in the CLI.
Looking down into FRR `vtysh -c "show run"` reveals that the neighbors are completely missing
# config
```
vyos@vyos# show protocols bgp 65010 neighbor 2001:db8::101:2
address-family {
ipv6-unicast {
peer-group AS65020
}
}
vyos@vyos# show protocols bgp 65010 peer-group AS65020
address-family {
ipv4-unicast {
soft-reconfiguration {
inbound
}
}
ipv6-unicast {
capability {
orf {
prefix-list {
receive
send
}
}
}
soft-reconfiguration {
inbound
}
}
}
capability {
dynamic
}
remote-as 65020
```
# commit
```
vyos@vyos# commit
[ protocols bgp 65010 neighbor 2001:db8::101:2 ]
must set remote-as or peer-group with remote-as defined
```