DNS: Create a Reverse Zone File

Record the IP address for the primary interface:

ifconfig -a

vim /etc/named.conf

Take the last three octets of the public IP address and enter them in reverse where you see xx.xx.xxx (such as 11.31.172). Insert the zone configuration just before the include statements at the bottom of the file:

zone "xx.xx.xxx.in-addr.arpa" {
   type master;
   file "/var/named/xx.xx.xxx.db";
}

Then run the named-checkconf command to verify the configuration.

named-checkconf

1. Create the reverse zone file and enter the following information:

   vim /var/named/xx.xx.xxx.db
   

2. Enter in the following:

   $TTL    86400
   @       IN      SOA     nameserver.mylabserver.com. root.mylabserver.com. (
                             10030         ; Serial
                              3600         ; Refresh
                              1800         ; Retry
                            604800         ; Expiry
                             86400         ; Minimum TTL
   )
   ; Name Server
   @        IN      NS       nameserver.mylabserver.com.
   ; PTR Record Definitions
   93       IN      PTR       nameserver.mylabserver.com.
   30       IN      PTR       mailprod.mylabserver.com.
   72       IN      PTR       mailbackup.mylabserver.com.
   ; Mail Exchange Records
   @		IN	MX	10	mailprod.mylabserver.com.
   @		IN	MX	20	mailbackup.mylabserver.com.
   

3. Run the named-checkzone command to check the zone file for syntax errors.

   named-checkzone mylabserver.com xx.xx.xxx.db
   

1. Change the file permissions for /var/named/xx.xx.xxx.db:

   chmod 760 /var/named/xx.xx.xxx.db
   

2. Change the group owner of the file to named:

   chgrp named /var/named/xx.xx.xxx.db
   

systemctl restart named

nslookup x.x.x.x localhost

Replace x.x.x.x with what ifconfig -a returned for an IP address earlier.