Setup a Basic Recursive Caching DNS Server and Configure Zones for Domain - Part 4

Testing the DNS Server

At this point we are ready to query our DNS server for local and outside names and addresses. The following commands will return the IP address associated with the host web1:

# host web1.sales.me.com
# host web1
# host www.web1

Query DNS on Domain Host

How can we find out who is handling emails for sales.me.com? It’s easy to find out – just query the MX records for the domain:

# host -t mx sales.me.com

Query MX Record Of Domain

Likewise, let’s perform a reverse query. This will help us find out the name behind an IP address:

# host 192.168.0.28
# host 192.168.0.29

DNS Reverse Query on IP Address

You can try the same operations for outside hosts:

# host -t mx linux.com
# host 8.8.8.8

Check Domain DNS Information

To verify that queries are indeed going through our DNS server, let’s enable logging:

# rndc querylog

And check the /var/log/messages file (in CentOS and openSUSE):

# host -t mx linux.com
# host 8.8.8.8

Verify DNS Queries in Log

To disable DNS logging, type again:

# rndc querylog

In Ubuntu, enabling logging will require adding the following independent block (same level as the options block) to /etc/bind/named.conf:

logging {
	channel query_log {
    	file "/var/log/bind9/query.log";
    	severity dynamic;
    	print-category yes;
    	print-severity yes;
    	print-time yes;
	};
	category queries { query_log; };  
};

Note that the log file must exist and be writable by named.

Summary

In this article, we have explained how to set up a basic recursive, caching DNS server and how to configure zones for a domain.

The mystery of name to IP resolution (and vice versa) is not such anymore! To ensure the proper operation of your DNS server, don’t forget to allow the service in your firewall (port TCP 53) as explained in Part 8 of the LFCE series (「Setup an Iptables Firewall to Enable Remote Access to Services「) and other articles in this same site such as Firewall Essentials and Network Traffic Control Using FirewallD and Iptables.

We hope you have found this article helpful – don’t hesitate to let us know if you have questions or comments. We always enjoy hearing from our readers!

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