Looks like the message a month ago on this was lost.
http://mail-index.netbsd.org/current-users/2003/09/14/0003.html

The problem is that when net.inet6.ip6.v6only=0, rpcbind is unable to bind
to the ipv4 sockets, it complains:

Oct 18 13:09:15 hysteria rpcbind: cannot bind udp: Address already in use
Oct 18 13:09:15 hysteria rpcbind: cannot bind tcp: Address already in use

If your running ypbind on the machine, ypwhich will have connection
problems. NIS still functions though.

The main reason to have net.inet6.ip6.v6only=0 was the message from the
install of netscape7/MozillaFirebird-bin. Do we still need that?

Ron Roskens