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Firefox DNS Lookup Hanging

LocutusEstBorg

Contributor
For the past few days I've been having this infuriating problem with Firefox. After browsing a couple of pages (or one very complex page) it just hangs on Looking Up <website>.

Opening anything in a new tab does not respond. It does not even open localhost or LAN IPs while it is stuck on Looking Up. After waiting for around 1 minute all the tabs instantly start loading. On analysis with Wireshark I found that it doesn't even perform the DNS lookup until after the 1 minute delay when everything loads.

I have disabled IPv6 lookups in about:config, tried adjusting the DNS cache settings in about:config, disabled IPv6 on the system. The actual DNS servers resolve in milliseconds so its not a problem with that. Opera and IE both work fine during the period when FF is stuck. I've also tried setting the DNS directly to OpenDNS instead of having the router DNS forward to OpenDNS. Also tried using the Domain Controller's local DNS server to forward. Also done a full uninstall/clean/reinstall of FF.

Now that I think about it, I am having the same problem on my office PC which I initially attributed to their connection. I'm running FF 3.6.3 on Server 2008 R2.

I have found 3 other threads on the internet where people are experiencing the EXACT same symptoms and have found no solution except to abandon FF in favor of Opera or IE. One bunch of them had the problem on Ubuntu.
 

FrozenIpaq

Justin B / Supp. Editor
Enforcer Team
Whenever I've experienced such lockups I've always just changed my DNS server in the IPv4 settings. I generally let it return to the default/automatic DNS server or use Google's DNS servers (8.8.8.8 and 8.8.4.4). Even though this seems to be a FireFox-only problem, have you tried switching your DNS servers?
 

LocutusEstBorg

Contributor
Yes I've tried OpenDNS, 4 of my ISP's DNS servers, and 4.2.2.2.

The fact that the DNS query does not even occur until after it unhangs implies the servers are fine. Even LAN IPs don't open. BTW there is no security software installed either.
 

FrozenIpaq

Justin B / Supp. Editor
Enforcer Team
Yes I've tried OpenDNS, 4 of my ISP's DNS servers, and 4.2.2.2.

The fact that the DNS query does not even occur until after it unhangs implies the servers are fine. Even LAN IPs don't open. BTW there is no security software installed either.
That's very odd indeed then, I'm not sure what to do besides re-installing the browser completely and hoping for the best. All the times I've run into this problem it was system-wide and not browser-specific so I have no further suggestions
 
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