CNAMEとAAAAを同じホスト名に設定できない件、RFC1912に載っていた。
RFC1912の2.4章。
2.4 CNAME records
A CNAME record is not allowed to coexist with any other data. In
other words, if suzy.podunk.xx is an alias for sue.podunk.xx, you
can't also have an MX record for suzy.podunk.edu, or an A record, or
even a TXT record. Especially do not try to combine CNAMEs and NS
records like this!:
podunk.xx. IN NS ns1
IN NS ns2
IN CNAME mary
mary IN A 1.2.3.4
This is often attempted by inexperienced administrators as an obvious
way to allow your domain name to also be a host. However, DNS
servers like BIND will see the CNAME and refuse to add any other
resources for that name. Since no other records are allowed to
coexist with a CNAME, the NS entries are ignored. Therefore all the
hosts in the podunk.xx domain are ignored as well!
If you want to have your domain also be a host, do the following:
podunk.xx. IN NS ns1
IN NS ns2
IN A 1.2.3.4
mary IN A 1.2.3.4
Don't go overboard with CNAMEs. Use them when renaming hosts, but
plan to get rid of them (and inform your users). However CNAMEs are
useful (and encouraged) for generalized names for servers -- `ftp'
for your ftp server, `www' for your Web server, `gopher' for your
Gopher server, `news' for your Usenet news server, etc.
CNAMEは他のいかなるデータと共存できません、特にNSと共存させると名前引けなくなりますよ、とな。