Nslookup query for NS records returns all of the NS records, but not all of the Host records

[Bob]

I have been to a few customers lately where the NS response is not giving
the complete list of Host records for all the corresponding NS records.

As an example, this manifests in nslookup by showing the full list of name
server entries:

microsoft.com nameserver = ns1.msft.net

microsoft.com nameserver = ns2.msft.net

microsoft.com nameserver = ns3.msft.net

microsoft.com nameserver = ns4.msft.net

microsoft.com nameserver = ns5.msft.net


But the list of "internet addresses" is not complete:

ns1.msft.net internet address = 207.46.245.230

ns2.msft.net internet address = 64.4.25.30

Doing a trace shows the same thing. The answer section shows a complete NS
list. The Additional Records Section shows the short list of Host records.
The host records for all of the servers listed in the NS list are present in
DNS.

Any ideas?

Thanks!

Bob

 

[Steve Duff [MVP]]

This is not an error. DNS servers are free to strip down
the additional records section -- mainly to shorten the
response to keep it within a single UDP packet.

Your example though would seem to be well under any
normal size -- maybe 200 bytes at most, and I can't offhand
see why a server would choose to truncate AR entries
at this point. Still in all, it is permissible.

The requester should just explicitly requery anything it
doesn't get back in one of the three sections. If it is
depending on an ARCOUNT > 0 that is an error.

Steve Duff, MCSE, MVP
Ergodic Systems, Inc.

 

[Jonathan de Boyne Pollard]

B> But the list of "internet addresses" is not complete:

It's not required to be. Resolving proxy DNS servers that want the "A"
resource record set of "ns3.msft.net." will instigate parallel query
resolutions to find it. (They'll also issue parallel query resolutions
for the other intermediate domain names, as a matter of fact.
Microsoft's delegation uses out-of-bailiwick intermediate domain names
and is thus effectively glueless. The data that are provided are
potential poison, and are discarded.)

<URL:http://cr.yp.to/djbdns/notes.html#gluelessness>