Quick question about Host records

[Jim Reid]

>>>>> "Don" == Don Stokes <don at news.daedalus.co.nz> writes:

    Don> Last time I looked, which was some time ago, NSI (and I'm not
    Don> sure about other registrars) key name server addresses on IP
    Don> address, and don't allow duplicates.  Thus, when you register
    Don> example.com with nameservers of ns1.example.com and
    Don> ns2.example.com, where the nses have the same IP addresses as
    Don> ns1.hank.org and ns2.hank.org, you'll find that the
    Don> delegation has magically changed to ns1.hank.org and
    Don> ns2.hank.org.

    Don> Annoying.

Maybe. But if they do this - I don't know or care - it prevents an
even more annoying problem. Suppose ns1.example.com was renumbered.
In the scenario you describe all that means is one glue record in the
.com zone is changed: the new A record for ns1.example.com. All the
other .com, .net and .org delegations that used ns1.example.com will
automatically go to the new IP address for that server. This is far
preferable to going through every delegation and changing each glue
record that might or might not be affected. It also saves subtle cache
pollution problems when glue for ns1.example.com in the parent zone,
.com, differs from what's in the child zone, example.com. Multiply
that by every delegation that could have its own NS and glue record
for the IP address of ns1.example.com and you should see the scale of
that potential problem.