To configure DNS functionality, browse to Network → DNS. The first tab DNS settings allows you to configure three forwarding DNS nameservers that will be used by the system to forwards unresolvable queries to. Click Update (at the bottom of page) to save.

You can check DNS functionality by browsing to Tools, Connection test. Fill in a domain name and hit 'Ping'. The first output line mentions the target domain name but also the resolved IP address. Compare this resolved IP address with the received replies from a working clients ping output. Note: not every host on the internet is configured to reply to ICMP ping requests (eg. fdxtended.com).

PING fdxtended.com (188.93.154.131) 56(84) bytes of data.

--- fdxtended.com ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 3999ms

PING google.fr (74.125.136.94) 56(84) bytes of data.
64 bytes from ea-in-f94.1e100.net (74.125.136.94): icmp_seq=1 ttl=47 time=16.9 ms
64 bytes from ea-in-f94.1e100.net (74.125.136.94): icmp_seq=2 ttl=47 time=22.0 ms
64 bytes from ea-in-f94.1e100.net (74.125.136.94): icmp_seq=3 ttl=47 time=16.4 ms
64 bytes from ea-in-f94.1e100.net (74.125.136.94): icmp_seq=4 ttl=47 time=22.4 ms

--- google.fr ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3005ms
rtt min/avg/max/mdev = 16.408/19.472/22.478/2.820 ms