Port 80 of my IIS web server stopped responding

[Mimi]

I have a P4 multiprocessor machine running W2K server SP3
with MS SQL Enterprise Server running. Our web site runs on
port 80 and are mostly ASP scripts. The site works fine for
several hours and then port 80 started not to respond to
client requests. All users see is the "Web Page cannot be
displayed - Cannot find server or DNS Error" error.
Sometimes after a few reloads, the web pages can be
displayed, but 99.9% of the time port 80 is not responding.

I ran some analyzing tools and found that client requests
did indeed reach our web server, but port 80 just didn't
respond to them 99.9% of the time. If I move my website to
port 8080, it works, but also just for several hours and
then it stopped responding just like port 80. About 1GB of
data was sent from our web server in a time period of about
6 to 7 hours. Restarting IIS or rebooting did not clear up
the "dead" ports. I couldn't even go to http://localhost
locally from my own server.

Anyone have any idea why the ports will suddenly stop
responding? Could it be network traffic load related? How
come not even rebooting clear up the ports?

Our server is a dedicated server loaned from an ISP. Would
it have to do with the ISP's network? They claim they
didn't impose any kind of traffic volume limitations. If I
change my machine to a different IP number, then port 80 is
responding again. So I don't think it's hardware related,
but I can't narrow the problem down any further.

This is really urgent. Our site is very unstable now and we
got lots of complaints from users. Any help is greatly
appreciated.

[James Howard]

First verify that IIS receives but does not send (as you have stated) on
port 80. Use network monitor to do this, look at
http://support.microsoft.com/?id=252876 . This should show you the incoming
and outgoing packets.

You can also use visualroute to see where 80 is stopping.
http://www.visualware.com/visualroute/livedemo.html

This should help you narrow down where the problem is located.

Thanks.

James Howard -- IIS Support Professional

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