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Old 09-05-2011, 06:36 AM   #1
Registered: Mar 2005
Distribution: Ubuntu 12.04 LTS
Posts: 249

Rep: Reputation: 16
My Linux laptop can no longer resolve DNS

I moved my Linux laptop from my home network, where everything seemed to be working fine, to another wireless network. All of a sudden, it no longer seems to be able to resolve dns (at least Firefox/Thunderbird).

My Firefox/Thunderbird in my Windows virtual machine works fine, and in Linux all other Internet things seem to be working fine (such as Skype, and pinging etc). I can even enter an IP address directly into Firefox and it will work, just typing an actual domain name such as won't work and give the standard 'cannot find server at ....' error.

What could have gone wrong here? (Reinstalling Firefox/Thunderbird to latest versions, and starting them in safe mode changed nothing.)

The only thing I can think of is looking at 'route' command output, which shows:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface    *        U     0      0        0 vmnet1     *        U     2      0        0 wlan0    *        U     0      0        0 vmnet8
default         UG    0      0        0 wlan0
Earlier I made a note to myself to run the following command, 'route add default gw', so I ran that command and ended up with 2 'default' entries in the output above. Still didn't get Firefox/Thunderbird to work. So removed as a default entry, and still didn't work. So then removed all 'default' entries and still didn't work. I'm so confused. (I didn't run 'sudo service NetworkManager restart' between every change, wasn't sure if I needed to.)

Any other changes to dns settings I may need to make? Not sure why things would have just stopped working when I changed the wireless network to which my Linux laptop is connected. But everything else seems to be working fine, except for DNS resolution in Firefox/Thunderbird.

If you could please help, I'd really appreciate it!
Old 09-05-2011, 06:55 AM   #2
Registered: Jul 2006
Location: Toronto, Canada
Distribution: gentoo
Posts: 33

Rep: Reputation: 17
This is not a problem with your routing table. Most likely the DNS addresses in /etc/resolv.conf are incorrect or non-existent.

If you are using DHCP on the new network verify that the DHCP server is supplying the correct DNS addresses.

If you have a static address assigned on your new network find out what the correct DNS addresses are and update your /etc/resolv.conf manually.
Old 09-05-2011, 07:00 AM   #3
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Registered: May 2001
Location: Belgium
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Since the problem is only in firefox, and you can ping, DNS is working.
Can you browse using another browser?
Try to disable ipv6 in firefox.

Kind regards
1 members found this post helpful.
Old 09-05-2011, 07:28 AM   #4
Registered: Mar 2005
Distribution: Ubuntu 12.04 LTS
Posts: 249

Original Poster
Rep: Reputation: 16
Thank you very much, marking thread as solved. People who stumble upon this thread can solve this problem by disabling ipv6 as described above in both Firefox and Thunderbird (must do it in both to get both working). Thanks again!


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