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How to add reverse IP Lookup on your IP's

Last Modified: Mar 25, 2010, 11:01 pm

Any modern version of DA will be able to do this through the interface.
Go to: Admin Level -> DNS Administration

Scroll to the bottom to the "Add Zone" section.

Enter your information normally:

domain name: server.hostname.com
ip: 1.2.3.4
ns1: ns1.hostname.com
ns2: ns2.hostname.com

where server.hostname.com is the hostname of your server.
The IP is your server IP (license IP)
and ns1/ns2 can be any NS your server uses.

Click the "Create Reverse IP Lookup" checkbox, then click "Add".

Wait a minute or so, then go into ssh to see if it worked:

dig -x 1.2.3.4

If it works, then you'll see a PTR record with your server name. If it doesn't you'll see a value that says "SOA" with likely your datacenters name beside it. This means that your datacenter has control over the lookup, so you'll have to contact them to set it up, as your server isn't queried when the lookup is done, even if it's correctly setup on your server.

For example, the IP of directadmin.com is 66.51.122.131. To check who has authority over the lookup, we can use SOA in the dig to see who controls the lookup on the IP:

server# dig SOA -x 66.51.122.131

; <<>> DiG 9.6.1-P1 <<>> SOA -x 66.51.122.131
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49196
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;131.122.51.66.in-addr.arpa. IN SOA

;; AUTHORITY SECTION:
122.51.66.in-addr.arpa. 1681 IN SOA tera-byte.com. hostmaster.tera-byte.com. 2010032522 3600 900 604800 1800

as we can see in this example, tera-byte.com controls the lookup of the IP. If we needed to change it, we'd contact the value just to the right, in this case hostmaster@tera-byte.com. We can confirm the lookup works because of the dig:

server# dig -x 66.51.122.131

; <<>> DiG 9.6.1-P1 <<>> -x 66.51.122.131
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36799
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 3, ADDITIONAL: 3

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

;; ANSWER SECTION:
131.122.51.66.in-addr.arpa. 3319 IN PTR ip-66-51-122-131.tera-byte.com.

The old fashioned/manual way to add the lookup (depreciated):

To add a reverse lookup on the IP 1.2.3.4, in your named.conf (RH: /etc/named.conf FBSD: /etc/namedb/named.conf) add

zone "4.3.2.1.in-addr.arpa" IN {
type master;
file "/var/named/hostname.db";
};

Note that the IP is written backwards (4.3.2.1).
In /var/named/hostname.db:

$TTL 0
@ IN SOA ns1.domain.com. root.domain.com. (
       2004022000
       7200
       3600
       1209600
       86400 )

    NS ns1.domain.com.
    NS ns2.domain.com.
    PTR domain.com.

Now the domain.com. that is in bold will be what is returned with the lookup. You can apply the hostname.db file to all IPs if you want, just add one zone for each ip in the named.conf using the above method.

*Note: If you do not have authority over the reverse lookup on the IP's you'll have to contact your datacenter to get them to do it for you. This means that your server might not be used at all for the reverse lookup on the IPs, making this tutorial useless :)