Reverse Lookups - Need Answer

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Odysseus - 22 Dec 2003 22:30 GMT

Hi,

I guess my message wasn't too clear. We host the PTR
records for the block of addresses that belong to us. In
effect, we are an ISP. Say we have addresses:

aaa.bbb.ccc.ddd

When our clients do reverse lookups of addresses that
belong to us, say:

aaa.bbb.ccc.123

they get the proper response. We maintain these PTRs and
we keep them up to date for our clients.

Our clients also use our DNS servers to do recursive
reverse lookups on addresses that do NOT belong to us:

eee.fff.ggg.hhh

These recursive reverse lookups fail.

I know that the PTRs exist because if I point NSLOOKUP
directly to the server that hosts it, I get the proper
response. I know that the host server is responding to
recursive reverse lookup requests because if I point
NSLOOKUP to one of our other, Linux based, DNS servers, I
get the proper response. It is only when I point NSLOOKUP
to the Windows servers that the reverse lookup fails.

>-----Original Message-----
>Hi,
>
>this is a PTR issue, as in it isn't being properly

updated;

>On the Windows NT servers that I maintain and on servers
>of my clients that need it, this is what I do.
>domain foo.com
>dns (private network, internal)
>a aaa.bbb.ccc.xx1
>b aaa.bbb.ccc.xx27
>c aaa.bbb.ccc.xx2
>
>Now what you need is the rDNS entries; you don't see the
>rDNS zone locally so you create your own.
>New zone, primary
>ccc.bbb.aaa.in-addr.arpa
>New record, PTR
>aaa.bbb.ccc.xx1 a.foo.com
>New record, PTR
>aaa.bbb.ccc.xx2 c.foo.com
>New record, PTR
>aaa.bbb.ccc.xx27 b.foo.com
>
>If, your DNS were being maintained by an ISP, you would
>need to have the rDNS modified by them to resolve their

>addresses to your DNS names.
>If they won't do it for free, consider changing ISPs
>
>>-----Original Message-----
>>Our data center has 5 DNS servers. Two are Windows and
>>three are Linux. The Windows servers are running NT 4.0
>>SP6a and MS DNS. The Linux servers are running BIND.

The

>>two Windows servers are listed with ARIN as the servers
>>which hold the reverse pointers for the IPs in our
>>assigned block. We have clients who are using these
>>servers for their DNS lookups. When they try to do
>>reverse lookups (i.e. for their mail servers) to IPs

that

>>are outside of our block, some of them fail. The

message

>>is:
>>
>>*** server can't find a.b.c.d: Non-existant domain
>>
>>If you set 'server' to be the DNS server listed by ARIN
>>for that a.b.c.d, you get the correct response. Also,
>>reverse lookups using any of the Linux servers work

fine.

>>So the server of record is responding to request for
>>reverse lookups and servers are capable of receiving
>>responses to a recursive reverse lookup. Only my

Windows

>>systems seem incapable of doing what they are supposed
>>to. Any ideas?
>>.
>>
>.

Reply to this Message

Kevin D. Goodknecht [MVP] - 22 Dec 2003 23:02 GMT

: Hi,
:
[quoted text clipped - 82 lines]
::
: .

You must name the zone according to the name that was delegated to you.
From the example you gave you did not correctly name your reverse zone.
Your reverse zone name must be the full name of the CNAME minus the PTR your
ISP delegated to you. Here's an example:
I'll give example using 192.168.0.0/29

You create the zone name as "0.0.168.192.in-addr.arpa" then put the record
1 PTR server.domain.com

Your ISP delegates the IP 192.168.0.1 to you by the CNAME
1.0.0.168.192.in-addr.arpa"

If the reverse lookup is not the full subnet name it will conflict with
other IPs in the subnet that you don't have.
To get a visual idea of the name that is delegated to you go to
www.dnsstuff.com and do a reverse lookup on your IP to see what the CNAME
referal is.

Signature

Best regards,
Kevin D4 Dad Goodknecht Sr. [MVP]
Hope This Helps
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