Why do I get "connection timed out" when I ssh into a server?

Question

Cannot connect with ssh to a server: connection timed out

I have always used ssh to connect to a server, then, suddenly, I can no longer connect to it.

$ ssh username@server1.example.com
ssh: connect to host server1.example.com port 22: Operation timed out

Note that this is happening only on a specific server, while I can still connect with ssh to the others.

What can I do?

Answer

The reasons can be:

• Wrong hostname or IP address

• Your local network (e.g. public network) does not allow ssh connections (try to connect to a different server to see if it works)

• Firewall rules set in your cloud provider network or a firewall in the remote server may block the connections, dropping all the packets before they reach the ssh daemon

• The remote machine is turned off

• The remote server is completely stuck and thus it cannot respond to the connection request (check the server CPU and other metrics from hypervisor or from a cloud dashboard and then restart the server)

You can also try to connect to the remote machine with a different method (e.g. from a browser console, offered by many cloud providers) instead of using ssh.