When doing a classicupgrade on a machine with multiple IP addresses, then one is choosen automatically - what is not always the one that it should use!
# samba-tool domain classicupgrade --dbdir=/usr/local/samba.PDC/private/ --use-xattrs=yes --realm=samdom.example.com --dns-backend=BIND9_DLZ /etc/samba/smb.PDC.conf
Looking up IPv4 addresses
More than one IPv4 address found. Using 10.1.0.49
There should be an option like '--host-ip=IPADDRESS'.
I haven't tested IPv6 addresses. But I guess it's the same (auto choice). In that case, there should be an additional option ('--host-ip6=IP6ADDRESS'), for that, too.
The workaround is to temporary shutdown the other interfaces, Samba should not use.
"interfaces=<ipaddress>" and "bind interfaces only=yes" does not do what you want?
# samba-tool domain classicupgrade ... --option="interfaces=lo eth0" --option="bind interfaces only=yes" ...
uses the IP from the given interface (of course not from localhost) and add the two parameters to the auto-created smb.conf.
I'm closing this enhancement request.