SSH server is by default configured to perform a reverse DNS lookup of your IP address every time you try to log in to the server. It could improve logging and security but would significantly increase login time.
Related: How to speed up SSH authentication
The login prompt could take a while to appear when reverse DNS lookup is enabled on the server, as the server will perform a reverse DNS lookup on the incoming connection's IP address before presenting the login prompt.
You can choose to enable or disable reverse DNS lookup in SSH by configuring UseDNS directive in the SSH server from the terminal.
Specifies whether sshd(8) should look up the remote host name and check that the resolved host name for the remote IP address maps back to the very same IP address. The default is “yes”.
$ sudo vi /etc/ssh/sshd_config [sudo] password for user:
Add the line if it doesn't already exist and remove # at the beginning of the line if the existing line starts with #.
$ sudo systemctl restart sshd
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