Network Weirdness

[David G. Mackay]

I've got an old AMD-K6-400 box that's been running FC3 that I've been
using as a router/firewall.  I recently ran up2date, and suddenly I
couldn't access several websites.  After playing around for a bit, I did
a clean install of FC4t3 on the box to see if that would resolve the
problem.  It didn't.  I can access most sites normally.  I can also plug
the Alcatel USB Speedtouch modem into a Win2k box, and access the
problematic websites.

I've done some archive searches to see if anyone else experienced this,
and came across the ecn problem, but my /proc/sys/net/ipv4/tcp_ecn is 0.
Ironically, one of the sites that I can't access is bugzilla.redhat.com
(although fedora.redhat.com is fine).

When I look at a tcpdump of the situation, I see the tcp connection
handshake followed by a GET request to the web site.  Instead of
returning the contents of the web page in response, I see a packet with
no data acking the get request packet.

Does anyone have any ideas?

Dave