21.2. Adding a Reverse Master Zone

To add a reverse master zone, click the New button and select Reverse Master Zone. Enter the first three octets of the IP address range that you want to configure. For example, if you are configuring the IP address range 192.168.10.0/255.255.255.0, enter 192.168.10 in the IP Address (first 3 Octets) text area.

A new window will appear, as shown in Figure 21-3, with the following options:

1. IP Address — The first three octets that you just entered in the previous window.

2. Reverse IP Address — Non-editable. Pre-populated based on the IP Address entered.

3. Contact —Email address of the main contact for the master zone.

4. File Name — File name of DNS database file in the /var/named directory.

5. Primary Nameserver (SOA) — State of authority (SOA) record. This specifies the nameserver that is the best resource of information for this domain.

6. Serial Number — The serial number of the DNS database file. This number must be incremented each time the file is changed, so that the slave nameservers for the zone will retrieve the latest data. The Bind Configuration Tool increments this number each time the configuration changes. It can also be incremented manually by clicking the Set button next to the Serial Number value.

7. Time Settings — The Refresh, Retry, Expire, and Minimum TTL (Time to Live) values that are stored in the DNS database file.

8. Nameservers — Add, edit, and delete name servers for the reverse master zone. At least one nameserver is required.

9. Reverse Address Table — List of IP addresses within the reverse master zone and their hostnames. For example, for the reverse master zone 192.168.10, you can add 192.168.10.1 in the Reverse Address Table with the hostname one.example.com. The hostname must end with a period (.) to specify that it is a full hostname.

A Primary Nameserver (SOA) must be specified, and at least one nameserver record must be specified by clicking the Add button in the Nameservers section.

After configuring the Reverse Master Zone, click OK to return to the main window as shown in Figure 21-1. From the pulldown menu, click Save to write the /etc/named.conf configuration file, write all the individual zone files in the /var/named directory, and have the daemon reload the configuration files.

The configuration creates an entry similar to the following in /etc/named.conf:

zone  "10.168.192.in-addr.arpa" {
        type master;
        file  "10.168.192.in-addr.arpa.zone";
};

It also creates the file /var/named/10.168.192.in-addr.arpa.zone with the following information:

$TTL 86400
@       IN      SOA     ns.example.com. root.localhost (
                        2 ; serial
                        28800 ; refresh
                        7200 ; retry
                        604800 ; expire
                        86400 ; ttk
                        )


@       IN      NS      ns2.example.com.

1       IN      PTR     one.example.com.
2       IN      PTR     two.example.com.