Trouble with External Lookups

krmdv at krmdv at
Thu Jun 8 05:08:15 UTC 2006

I can do everything with my IP address except get a reverse lookup off 
of it. I can nslookup connect to the IP address and it responds.  I 
found an article on the next that had the same error described with my 
ISP (SBC/ATT).  I called SBC and they are putting the reverse 
delegation in for my IP Block.  The change should take 24 to 72 hours 
so I should hopefully be good to go.  If you can think of anything else 
I can try, please let me know.  I havent touched DNS in a couple years 
so things are slowly coming back.

When I perform nslookup on my ip address outside my network I get Can't 
find IP addy Non Existent Domain.  If I do an nslookup 
from inside my domain I get:

** server can't find NXDOMAIN

I can run nslookup then connect to the IP address so there doesnt 
appear to be any firewalling issues.

All of this investigation lead me to the ISP not delegating reverse DNS 
on my IP Block.  Let me know if you any thoughts on this being 
something else.

Thanks again!


-----Original Message-----
From: Barry Margolin <barmar at>
To: comp-protocols-dns-bind at
Sent: Wed, 07 Jun 2006 22:22:01 -0400
Subject: Re: Trouble with External Lookups

  In article <e67rnf$2aa2$1 at>, krmdv at wrote:

> Thanks Barry for the heads up on the email etiquette its been a while
> since I have last posted to mail lists. I will provide the proper
> information next time. Anyway, I actually solved the problem earlier.
> It turned out to be a Reverse DNS Delegation problem with my ISP. 
> will be forwarding my IP Block onto my name servers and that should
> take care of the reverse lookup problem Im getting on my external IPs.

Yeah, I almost put that guess in my response.  But I figured I would
wait for your response, to see whether you were querying your server
directly or not.  If you were querying your own server and getting an
error, it wouldn't be a delegation issue (unless you're using RFC
2317-style delegation).

Barry Margolin, barmar at
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

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