I have spent over 30 years researching and designing networks - from the time before there was an internet, or tcp/ip, or even ethernet - so I'm not exactly a noob with regards to networking. But this problem has me stumped. And I've had this same problem before, with previous version of Fedora, and it seemed to get resolved only when I upgraded to a newer version of Fedora.
Anyways, here's the problem:
I have three computers. All are connected to the same switch, which is connected to my firewall (a cisco pix), which is connected to my DSL router. Two of these boxes are running Fedora 17 (kernel 3.5.0-2.fc17). Both have the linux firewall disabled, as well as selinux. The third box is running WinXP.
Everything was fine until a few days ago: I started seeing that I could not access certain sites. One of these sites is mozilla.org (another is facebook.com). I can ping the sites, and I can open a tcp connection to them (eg, telnet to port 80). But if I send an HTTP GET - either with firefox, or just wget - no response comes back.What's really weird, though, is that on the WinXP box I have no problems accessing these sites. (Note again that all three are connected to the same ethernet switch.)
So, after a process of elimination, it seems there must be some issue with linux networking (more specifically, its HTTP) and these sites.
Other things I've tried:
- replaced my pix firewall with a simple netgear gateway. Same problems.
- changed wan IP address ( I have three, and tried all of them).
- Checked with a friend who has the same ISP, and is running F17. He has no problems.
- sniffed the network traffic on one of the Fedora boxes, via wireshark: saw tcp req sent, tcp ack received, HTTP GET sent, but only tcp ack (for the first tcp req) retransmitted. Saw basically the same thing on the wan side of the firewall.
Weird, huh? This is driving me nuts. Not only can I not accessed these sites, but I just can't understand why not. I must be missing something very simple somewhere.
So any help will be greatly appreciated.