Domain only reachable over browser as long as ping is running *on the server* (also ssh doesn't work)

I have a remote machine on which I run Debian and Apache. Recently, a strange problem occured.

It started with me not being able to log in by ssh anymore (I simply get a timeout) and my domain not being reachable over the browser. I think I couldn't ping it as well but I'm not sure about this. As of now, ping works.

Using the control panel of the provider, I am still able to log in. ip link shows that the interface is UP. The strange thing is that while I run ping google.de on the server, the domain suddenly is reachable from the browser. After aborting the ping, the domain stops being reachable again. SSH works in none of the cases.

My first goal is to understand this strange behaviour, my second goal is to get SSH (and my domain) back to work.

This could be a duplicate ip-address issue. Some other host in the subnet has snatched your ip-address. Ping works because it is stateless, and whatever host gets the ping request, will send the ping reply.

Then, when you ping google from your server, your host will claim the ip-address, and the provider's routers/firewalls will update their arp-table.

If you check the /var/log/syslog file it should report that some other host is using your ip, and you should also be able to see the other host's mac address. If you find this info, you need to contact your provider to rectify the issue.