For some reason from some computers and some networks our website is extremely slow.

From work under Windows and Linux boxes home page loads 3-5sec.
From home
under Windows XP - 3-5sec
under Linux(Ubuntu) - 5min!
another Windows XP 5min also
under Mac 5-10sec, but it might be because computer is slow

My friend test our web site from his work and said:
"- It work so some linux boxes
Windows YES
MAC on some of them YES on some NO
CentOs 5.1 NO
Redhat- kernel 2.6.9 YES
Fedora 8 NO"

What is the problem? Is this our problem or provider problem?

Thank you

What does this YES and NO mean? And what was the test?

Where is the homepage hosted?
How are you attempting to connect?
Are all the boxen connecting via identical means? (Compare modems with modems - xdsl? same speed? over network? compare on same network.)

Check machine specs - if the page has a lot of rich content, then slow connections will connect slowly. Try it out on a simple web page with no bells and whistles?

YES and NO means Fast and Slow connection respectively. Test was just open page in the browser. Also tried get page through GET.

Very simple cgi script which generates very simple html.
Connection through web browser.

Hosted on Debian, Apache2.
2 computers in the same network with the same OS has different connection speed. One 3-5 sec and the other up to 5min.

Cache in the browsers is turned off.

Check by telling them to refresh.

Anyway, you need to talk to the server sysadmin. Confront her with the two machines you just told me about. Or is it you?

This kinda sounds like it could be a DNS issue. Slowness like this can be caused by faulty DNS entires. On the linux boxes check what is in resolv.conf If every computer that take 5 mins to load the page has the same DNS server that might be it. Just an idea.

This is very strange, because scp, ping and everything else works just fine. Only web doesn't work.

Also there is one more web server connected to the same switch and I can't access to this server through the web. But ssh works fine.

Looks like switch problem. Not particular pc box problem. Will try to reconnect server to the other switch and see what will happen.

We figured out what was the problem by changing rules at firewall.

For others to avoid the same mistakes - which firewall, what changes?

Please describe what it was about the firewall settings causing the slow speed, and if the firewall was something an a server or the other hosts or what.

I actually didn't get it. Top level administrators set some firewall settings - close all ports and left just opened http, smtp, ftp and few others. We were debuging using tcpdump and figured out that destination server reply for every try to connect but server with the firewall accept only first attempt to connect and reject all the rest. Then sysadmin wrote "keep state" somewhere in the Packet Filtering rules and it works! Sorry i don't know more details.