I've been setting up an experimental Linux Server (RH 9.0) with OpenSSHd, Apache, ProFTPd, MySQL and PHP activated for my employer.

The server has a static IP-address and a valid DNS entry, and from time to time it works just fine, it responds to DNS and IP calls with no problem at all - including all servers.

Then, after a couple of hours, I lose the possibility to connect to the server from the outside world. It just doesn't respond, and I get time out-messages on SSH and not responding-messages on HTTP.

The "solution" for breaking the server's isolation is to call it from a machine on the same local network (ie another corporate server).

For instance, I've found solutions to include

a) make an SSH-call from a machine with IP xxx.xxx.xxx.2 (my server being xxx.xxx.xxx.8), and my server starts communicating with other networks after a couple of seconds

b) send a dummy e-mail from our mailserver (xxx.xxx.xxx.5) to my server (to a non existant recipient, causing the mail to bounce - my firewall is for that matter configured to drop mail, and no mail servers are activated).
But nevertheless I get the same result as in a) - a functioning server...

I've checked my log files and I can't find anything quite matching the time the server stopped responding.

Is there anyone who experienced a similar problem?