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 show protocols bgp 65000 { address-family { ipv6-unicast { network 2001:dba::/32 { } } } neighbor 2001:db8:1::2 { address-family { ipv6-unicast { peer-group AS65001 } } } parameters { log-neighbor-changes router-id 172.18.254.202 } peer-group AS65001 { address-family { ipv6-unicast { } } remote-as 65001 } } static { route6 2001:dba::/32 { blackhole { } } }
commit
vyos@vyos# commit [ protocols bgp 65000 ] [ protocols bgp 65000 neighbor 2001:db8:1::2 ] must set remote-as or peer-group with remote-as defined
FRR
vyos@vyos# vtysh -c "show run" Building configuration... Current configuration: ! frr version 7.0.1-20190514-01-gcd305c0 frr defaults traditional hostname vyos log syslog informational agentx service integrated-vtysh-config ! ipv6 route 2001:dba::/32 Null0 ! router bgp 65000 bgp router-id 172.18.254.202 bgp log-neighbor-changes neighbor 2001:db8:1::2 remote-as 65001 ! address-family ipv4 unicast network 10.0.0.0/9 network 10.128.0.0/9 exit-address-family ! line vty ! end
ugly workaround
as soon as I change my configuration like the following everything works - but now I have multiprotocol configuration which I tend to avoid
vyos@vyos# show protocols bgp 65010 neighbor 2001:db8::101:2 address-family { ipv6-unicast { peer-group AS65020 } } peer-group AS65020