We have stub-zones configured on our gateway for reverse IPv6. Our ISP doesn’t delegate rDNS but we still want to lookup addresses (at least on the local side). To do so I configured a stub-zone from unbound, our local caching DNS, to our own rDNS authoritative server. Apparently unbound wants an IPv6 for its IPv6 rDNS queries to the stub-zone. Since IPv6 is not always working I solved that using the local interface. That is, the rDNS authoritative listen on localhost:5353 and unbound uses this as its stub-zone addresses.
On the authoritative (here NSD):
ip-address: ::1@5353 ip-address: 127.0.0.1@5353 do-ip6: yes
On unbound, note that we need
do-not-query-localhost: no to allow queries on localhost:
do-not-query-localhost: no stub-zone: name: 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa. stub-addr: ::1@5353 stub-addr: 127.0.0.1@5353