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Reverse DNS to IP

Posted on 2004-04-26
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Last Modified: 2011-09-20
How can I setup a DNS record so that the Reverse DNS for an IP resolves as the IP.  I am using bind and I keep getting and error that the PTR records 123.123.123.123 does not point back to the IP.

db.132.123.123.123.in-addr.arpa

132.123.123.123.in-addr.arpa IN SOA mydomain.com. admin.mydomain.com. (
                                2004042605 ; serial
                                3600       ; refresh (1 hour)
                                600        ; retry (10 minutes)
                                86400      ; expire (1 day)
                                3600       ; minimum (1 hour)
                                )
                        NS      ns1.mydomain.com.
                        NS      ns3.mydomain.com.
$TTL 86400      ; 1 day
                        A       123.123.123.132
                        PTR     123.123.123.132.
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Question by:hexfusion
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6 Comments
 
LVL 26

Expert Comment

by:jar3817
ID: 10921271
I just tried it on my server with this config:

file: /var/named/10.152.74.rev
------- paste ------
$TTL 3600
@       IN      SOA     dns.example.com. root.example.com. (
                2001082001 10800 3600 604800 86400 )
@       IN      NS      dns.example.com.
1       IN      PTR     10.152.74.1.
------ end paste ----

and this is the output of a reverse lookup:

---paste----
[root@example named]# host -v 10.152.74.1
Trying "1.74.152.10.in-addr.arpa"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13591
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;1.74.152.10.in-addr.arpa.      IN      PTR

;; ANSWER SECTION:
1.74.152.10.in-addr.arpa. 3600  IN      PTR     10.152.74.1.

;; AUTHORITY SECTION:
74.152.10.in-addr.arpa. 3600    IN      NS      dns.example.com.

Received 97 bytes from 10.152.74.254#53 in 0 ms
---- end paste-----

Is that what you are trying to do?
0
 
LVL 2

Author Comment

by:hexfusion
ID: 10921318
If I do a reverse on 10.152.74.254

http://www.dnsstuff.com/tools/ptr.ch?ip=10.152.74.254

Answer:
No PTR records exist for 10.152.74.254. [Neg TTL=604800 seconds]

I get
Answer:
123.123.123.132 PTR record: 123.123.123.132. [TTL 86400s] [A=None] *ERROR* A record does not point back to original IP.

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LVL 26

Expert Comment

by:jar3817
ID: 10921942
You wont get an answer for my address (its an internal address range (not public)).

Try using a real dns resolver, not that webpage.  I think that error message you are getting is generated by the webpage because there is no A record for the "name" 123.123.123.132.

you mentioned this is bind, so open up a console and type "host 123.123.123.132"  and see what the output is.
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LVL 40

Accepted Solution

by:
jlevie earned 2000 total points
ID: 10923471
First of all you can't have a in-addr.arpa zone for a single ip, which is what 123.123.123.132 would be. An in-addr.arpa zone is one of; a Class A, B, or C network, or if properly delegated, a subnet of one of those. When using one of the RFC 1918 reserved networks you are pretty much free to do what you like with it or delegations thereof. However, when dealing with routable networks the holder of in-addr.arpa authority for that netblock must properly delegate authority to your name server for a reverse lookup to work against your DNS server.

I suspect that you are attempting to provide a reverse lookup for a routable IP and the holder of the netblock that IP lies in hasn't delegated the authority for that subnet to you. The choices then become either to gain that authority or to ask the holder of the in-addr.arpa authority to host the PTR record(s) for your IP(s).
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