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Multiple PTR records?

Posted on 2010-08-19
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Last Modified: 2013-11-25
Hello

I had a question re. DNS I was hoping someone could help me out with.

i) Is it possible for a host to have more than PTR record?
ii) Is it possible for an IP address to have more than one A record?

The answers should be relevant to:

i) Microsoft AD DNS
ii) UNIX DNS (QIP)
iii) WINS

Many thanks!
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Question by:kam_uk
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by:Glen Knight
Glen Knight earned 400 total points
ID: 33478394
An IP Address can have as many A records as you like.
you can also have more than one PTR records, why you would want to I don't know.
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by:kam_uk
ID: 33478677
Hi Demazter

Thanks..

If I didn't have access to the DNS system itself, do you know how I can find out what those multiple values were? I assume if I used PING and NSLOOKUP, I would only be returned one value at a time?
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by:DrDave242
ID: 33486912
Ping will only return one address, but nslookup will list them all.
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by:kam_uk
ID: 33513239
Thanks, but what command would I need for NSLOOKUP to list them all?

Just

NSLOOKUP <IP>

?
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DrDave242 earned 1600 total points
ID: 33515548
I prefer to use nslookup in interactive mode, but I've been doing some testing, and here's what I've found:

(Note that these tests were performed on a Windows 2003 R2 DC.  It's possible that 2008 and/or 2008 R2 will give different results, and I know next to nothing about UNIX, BIND, or anything of that sort.)

"Nslookup <hostname>" will return all IP addresses in host records with that name.
Nslookup in interactive mode (ie., typing "nslookup" <Enter> "<hostname>" <Enter>) will do the same.
"Nslookup <IP_address>" will only return one hostname for that address.
Nslookup in interactive mode does two things: If you simply enter interactive mode and then type the IP address, it will only return one hostname.  However, if you explicitly set the query type to PTR ("set q=ptr" in interactive mode) and then enter the IP address, it will return all PTR records with that address.  There's probably a way to set the query type in non-interactive mode as well, but being a fan of interactive mode, I don't know of it.
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by:kam_uk
ID: 33516239
Thanks... Just to be sure what you mean about interactive mode for multiple PTR returns, would be something like this:

Nslookup

Set type=ptr

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by:DrDave242
ID: 33516254
That's it exactly.
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