Interesting DNS problem.

I've just been hired to fix problems at a small ISP. One of their customers has listed several nameservers with a single IP.

I didn't know this was possible. I thought there was a 1 to 1 relationship with nameserver names/addresses. I'm trying to figure out if this is or will be a problem.

Any input would be greatly appreciated.
Bob Martin

Connected to
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Whois Server Version 1.3

Domain names in the .com and .net domains can now be registered
with many different competing registrars. Go to
for detailed information.


Paul Vixie can probably better address this than myself, but I will
mention that with my experience with running, the main
problems you run into from an operational standpoint are:

1) When you need to change IP addresses for the nameserver you now have to
coordinate the change on a hundred different entries instead of just one.
If you use a single name, you just change that entry.

2) Depending on the exact situation, the nameserver may or may not know
that it is authoritative for the domains since it may or may not realize
that a given nameserver name is itself. Especially if there are
resolution issues with the name in question at load time. Again, Paul
Vixie may be able to better respond to this one. At, we
tell people it's permitted to use their own name for our secondary server
(if they ask) - but ask that they list the official name for our
nameserver in the NS records for the zone to make sure we answer
authoritatively. That said, we do try to discourage this because we see
it as potentially causing more harm than good.


Had been possible for about 3 years, maybe more. And remember before you
could have the same as well if nameserver with same ip was registered in
multiple TLDs, but it was a problem when Verisign still had .COM zone run
on the root name server so that is the reason why it was not officially
aloowed, but it should not be a problem any more. The only thing to worry
about is that if you have multiple nameserver on the same ip, when you
renumber then you have to remember to change each one of those nameservers
separately and with too many of them its going to be a pain in the --).

BTW - that is nothing, how about multiple ips registered in whois and
TLD zone for the same nameserver? (and not to mention fun you might have
if you ever need to renumber and want to change just one of those ips -
those registrar & registry techs might have interesting time trying to
figure out how to do it with EPP or even worth with RRP...