Recently, we’ve setup an Ubuntu server behind CloudFlare that needed to listen for SSH connections.
Unfortunately, CloudFlare does not allow connections to the default SSH port which is 22.
So, to achieve what it was needed we either had to change the port that the SSH service was listening to or add an additional port.
We decided to go with the option of listening to multiple ports for SSH connections, this way users that were also behind the CloudFlare CDN could still continue to use their SSH clients without being forced to define the connection port manually.
The port listening setting is available in /etc/ssh/sshd_config, using sudo we edited the file with a text editor and searched for the following lines:
# What ports, IPs and protocols we listen for Port 22
Right after the line that contains Port 22, we added another line for the new port (to see the list of all available open ports on CloudFlare, check this post)
And the file became as follows:
# What ports, IPs and protocols we listen for Port 22 Port 2053
Afterwards, we restarted the SSHD service to apply the changes by executing the following command by using sudo:
systemctl restart ssh;