Configuring a Secondary DNS Server

The configuration of a secondary DNS server is similar to that of a primary DNS server, although there are some important differences:

• There are no zone files to create. These are automatically copied from the primary DNS server when the secondary server is configured and started for the first time.

• The status of this server for all zone entries in /etc/named.conf is slave , except for the root domain.

• There is an extra entry in the /etc/named.conf file that identifies the master server IP address. This specifies from where the zone files are to be copied.

In the previous section, the domain xyz.com was used to configure a primary DNS server. The sample /etc/named.conf file shown here is for a secondary DNS server in the same domain:

 options {         directory "/var/named"; }; zone "." in {         type hint;         file "named.ca"; }; zone "xyz.com" in {         type slave;         file "db.xyz";         masters { 192.168.28.28; }; }; zone "28.168.192.in-addr.arpa" in {         type slave;         file "xyz.rev";         masters { 192.168.28.28; }; }; zone "0.0.127.in-addr.arpa" in {         type master;         file "named.local"; }; 

Each DNS server is always the master for the loopback reverse resolution zone ( 0.0.127.in-addr.arpa ) because it refers to the local loopback address. This would not be copied from a primary DNS server. You should be aware of this in case you have to analyze a /etc/named.conf file in the exam.

Note that the root domain file, named.ca , is not automatically copied from the primary DNS server; it should be manually copied once during the configuration.