[clue-tech] Inability to go to Google (and other websites) from Firefox and Qwest MSN DSL on Linux -SOLVED-

[Chris Hirsch]

Here's one for the archives:

Just for grins put on your troubleshooting hat and let's see if you get
the right answer:

For quite a while I had a client who had switched from Windows to Ubuntu
and was unable to get to Google, Slashdot and many other web sites using
Firefox.

His setup is Ubuntu 5, Qwest MSN DSL directly connected to an Actiontec
router. When in Ubuntu he can do DNS lookups for google, can ping google
but if you use Firefox it will just eventually time out. SOME websites work.

If you boot into Win2K and use Firefox (on a separate laptop) Google
comes up perfectly. If you boot the laptop into FC4 and go to Google it
has the same problem: Firefox will time out after a while.

As it turns out, I have a very Linux-savy co-worker who just upgraded
from dialup to Qwest MSN DSL and he was having the same problems when
using Linux. Windows works fine.

So of course the conspiracy theory of MSN using some sort of Windows
specific proxy came up but no info there. Let me tell you...we were SURE
that was it ;-)

It was then thought that it was an MTU problem because MS typically sets
the MTU by default to 1394? (or so) whereas Linux uses 1500. This was
tried and still no dice. We were also sure this was the problem too.
I've seen MTU problems with IPSec where you can get to some sites but
not others.

My co-worker then installed an IPCop firewall and he then realized that
he could see Google from Firefox under Linux. This one took me by
surprise but it did help start me on the right path (and google searches).

So......have you figured it out yet? If so, kudos to  you!


The problem: By default Firefox supports (and enables IPv6 DNS lookups)
since MS OSes don't really support IPv6 these lookups must all fail in
MS  and Firefox must use IPv4 lookups by default. For Linux however IPv6
is usually enabled by default and so Firefox will attempt these IPv6 DNS
lookups.

Here's the kicker: Since my co-worker went to IPCop, he is now using a
caching DNS server so the IPCop DNS server must translate IPv6 attempts
to IPv4 and all is well. My client however, was using the Actiontec
directly and so DNS lookups went into the MSN DNS servers that
apparently don't translate IPv6 to IPv4 and those were what were causing
the hangs (Feel free to clarify anything wrong with my technical
explanation my IPv6 knowledge is small).

The solution is posted here
http://www.linuxforums.org/forum/linux-newbie/57813-browsing-issue-firefox-1-5-a.html
which is how to turn off IPv6 DNS lookups in Firefox.
*Turn off the IPv6:*
* type about:config in the Navbar/address bar and hit Enter
* then look for network.dns.disableIPv6 - right-click and toggle to true
* restart Firefox
* try to connect

FYI if you are seeing slow response times with ssh connecting to a
server this is a related problem (ssh is attempting IPv6 DNS lookups and
taking a while to timeout).


I look forward to any responses as this was one of the trickier problems
I've had to troubleshoot in a while.


Chris
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