[dns-operations] 127.in-addr.arpa zone

Mike Jones mike at mikejones.in
Sun Aug 21 15:05:04 UTC 2011

Hi all,

I doubt it causes any operational issues anywhere with this specific
zone, but I was testing a diagnostic tool i was working on and did a
PTR lookup on and noticed the following:

a.in-addr-servers.arpa. is serving 0.0.127.in-addr.arpa. with a PTR
record for resolving as "localhost"
d.in-addr-servers.arpa. is serving 0.0.127.in-addr.arpa. with NXDOMAIN
e.in-addr-servers.arpa. is serving 0.0.127.in-addr.arpa. with a PTR
record for resolving as "localhost" on IPv6,
and NXDOMAIN under in-addr.arpa. on IPv4 (hu?)
the other in-addr servers are all returning NXDOMAIN under the
in-addr.arpa. zone

The IPv4/IPv6 differences observed on E also leave open the
possibility that different anycast nodes under the same address may be
configured differently. For the record my IPv4 queries to E go to
au-anysec1.apnic.net and IPv6 to hk-anysec2.apnic.net.

I also had a look at
and get NXDOMAIN from all servers except e.ip6-servers.arpa which
responds with localhost (on both IPv4 and IPv6). Although the AS112
website mentions plans to delegate this zone to the AS112 project.

Anyone know if there's any reason for the inconsistency, or just
something nobody has really thought about and they just did whatever
when setting up the servers? I had actually assumed 127.in-addr.arpa
would have been delegated to the AS112 servers but I guess it doesn't
see the same kind of traffic due to most hosts already having a
localhost entry in their hosts file.


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