Slow firefox DNS

I estimate 4-5 seconds while firefox is reporting that it is "looking up" some host, and since some sites link to other sites for ads and images and who knows what, this makes using the internet from home pretty unpleasant. Using nslookup or dig, I see that DNS lookup take on the order of 50 milliseconds or so, so something does not add up.

I don't see any of this from my machine at work (at the university over a fast LAN), and frankly don't think I should at home either, but it is clearly something peculiar to firefox.

Well, I found a post online that suggested the following, and the difference was like night and day:

• Enter about:config into the URL entry field in firefox.
• Enter network.dns.disableIPv6 into the Filter: entry field.
• Change the value of this setting from false to true.

I was getting ready to get on the phone and give Qwest hell, (they deserve it for any number of reasons) and maybe there are still culpable in some way, but the above trick has certainly solved my problems for now. If this was something that Qwest was screwing up on and was unwilling to fix, I was ready to dump them, and cough up the money for a cable modem and make the switch.

I have also begun using Googles DNS servers:

nameserver 8.8.8.8
nameserver 8.8.4.4

One question still nags at me. Why does firefox at work run so fast with IPv6 enabled, but firefox at home over DSL needs to have IPv6 turned off? At work, I talk directly to our linux DNS servers. At home I talk through the crappy actiontec DSL modem to whatever DNS servers I am using (the Google servers at the present time). DNS to the google servers was badly slow before turning off the IPv6 action in firefox.

If I ever figure it out, I will let you know!