Ping does not work at all. When adding a laptop to the router the server is connected to (with dynamic IP) the laptop can connect to the internet.
Another server (running Ubuntu 6.10 with ISPConfig) connected to the router does not have a problem either. It's only the one server that has a problem.
I compared ifconfig between the two and there is no difference. Also, logging in to the ISPConfig management panel is not a problem at all either.