Comment 10 for bug 663395

To test DNS, you can use nslookup. It's a commandline tool for querying dns servers.

1) Open up a commandline and type in "nslookup" and pressing enter (a prompt should appear waiting for input)
2) type in url's like google.com, facebook.com or ubuntu.com, etc... etc... followed by and enter
3) You should be getting responses in about under 1 second for each query
4) exit with "exit"

If you get near instant responses, that means that DNS (over ipv4) is ok.

Should you get very long response times, you're probably experiencing a different kind of issue than explained in the bug report.
If this is the case, try changing Dns servers, for example OpenDNS.

You can switch DNS server(s) by manually editing your connection in Network Manager, and selecting IPv4 "Automatic, only addresses".
You should be able to edit the "DNS server" field.

In there you can enter the following IP's: 208.67.222.222, 208.67.220.220
and repeat the testing process with nslookup

Again if that fails, than I believe you are experiencing a different kind of problem.