RHEL7: Configure a caching-only name server.

Note: This is an RHCE 7 exam objective.

Presentation of Caching-only Name Server

A cache-only name server keeps a cache of all the results of the previous requests to the root DNS servers.

Configuration Procedure

Install the bind package:

# yum install -y bind

Edit the /etc/named.conf file and change the listen-on option from 127.0.0.1 to any:

listen-on port 53 { any; };

In the same file, change the allow-query option from localhost to any:

allow-query { any; };

In the same file, disable the dnssec-validation option:

dnssec-validation no;

Check the configuration file:

# named-checkconf

Add a new service to the firewall:

# firewall-cmd --permanent --add-service=dns
success

Reload the firewall configuration:

# firewall-cmd --reload
success

Activate the DNS service:

# systemctl enable named

Start the DNS service:

# systemctl start named

Time to Test

Check the configuration:

# nslookup cnn.com 127.0.0.1
# dig @127.0.0.1 cnn.com

Additional Resources

You can also read this nice article from Zytrax.com about the different DNS Configuration Types. If you want to go any further, check the master DNS server tutorial.