Connection losses after a while


I have a very strange problem with one of our openSUSE boxes. It is located behind a corporate firewall and we are just having SSH access to the system. Since a few weeks we are loosing the connection to the server from time to time. When the system is rebooted everything runs fine. There is no error in the log files.

But I am not sure if the system has been locked up. During the time we have no access, the only thing that appears in the syslog are some MARK messages. Does this mean the system is running fine but just has no connection to the net? I was assured that there were no issues on the peripheral network devices… Is there maybe an issue with the network interfaces? But how to test from remote…

I don’t have any clue what to do from here on

I am grateful for any hint!