How to disable reverse DNS lookup in SSH

SSH server is by default configured to perform reverse DNS lookup every time you try to log in to the server. It cloud slightly improve logging and security, but could significantly increase login time.

Basically, the login prompt will take a while to appear as the server will perform reverse DNS lookup prior to presenting the login prompt to the connecting user.

You can fix this issue by setting the UseDNS directive to no on the SSH server at the terminal.

Disable reverse DNS lookup in SSH:

1. Launch terminal application.
2. Open SSHd configuration file using a text editor.

   $ sudo vi /etc/ssh/sshd_config
   [sudo] password for user:

3. Search for UseDNS directive and set the value to no.

   UseDNS no

   Add the line if it doesn't already exist and remove the # at the beginning of the line if exists.

4. Reload or restart SSH server service.

   $ sudo systemctl restart sshd

   How to restart SSH service