Some sites fail to load one of my computers [solved]

[iceaway]

I'm having a strange network related problem on one of my computers. One site that works poorly is facebook. I can load the first page, but when I try to login the browser just sits there loading, but nothing happens. The same thing happens to some other sites as well (but not all), at first I can load the site, but when I try to login it gets stuck. If I try to use another browser, the same thing happens, the first page loads, but as I try to login it just tries to load the page forever. I have tried creating a different user on the computer, but to it has the same problems. My network setup is as follows:

computer -> [wire] -> switch -> [wire] -> wireless access point -> [wireless] -> wireless router -> [wire] -> internet

I have another computer running windows 7 connected to the switch, and I'm not experiencing any problems there. I have several other computers connected directly to the wireless network, and they aren't experiencing any problems either. I have tried looking in the settings of the router and wireless access point to see if the sites could be blocked, but I haven't found anything.

Any ideas?

[krinn]

You should check two points, your card MTU and its metric.

The MTU depend on connection type, for classic ethernet it should be 1500 (1492 for ppp) less than that you may get lost packets (and the effect a site load slowly or not at all, while some other works)

the metric is number of hop (switch/router) in your road to internet, so for you it should be set to 3 (switch, access point, wireless router), most router can detect that but some poor drivers sometimes fail to query the correct value.

You may check wiki or some other media for info correctness. I'm not sure howto solve the metric problem, but the MTU one can be set easy.

Both could be check with ifconfig output

[iceaway]

I've checked both the MTU and metric, and unfortunately the MTU is 1500 and metric is 3, so that is not the problem.

[Hu]

What is the MTU on a working system? MTU should be set as high as reasonably possible and then negotiated down via PMTU discovery, but if an intervening device breaks PMTU discovery, the observed behavior could occur.

[krinn]

2 others possible problems i could think of would be DNS (bad server and you may wait for timeout until the resolv is done properly), something you could change using google public dns to test (8.8.8.8 and 4.4.4.4 if i remember well)
and IPv6 hell (many routers still doesn't handle well ipv6 encapsulate in ipv4, some didn't even know what ipv6 is) if some of the hops fail and others work, you'll get delay as the packet are resend and resend, until a proper path (one handling ipv6) is pickup.

I don't know where as i don't use ipv6, but you have a flag in /sys certainly to disable it temp, or rebuild a kernel without ipv6 or if build as module unload it.

That's just guess, i would have put all my bets on MTU tbh :/

[Odward]

[iceaway]

[iceaway]

I think I have solved it now. I was looking through the settings on my router, and discovered that the MTU was set to 1492 there. Changing it to 1500 appears to have solved the problems. I never thought about that being a setting available on the router too.... doh!