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.
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”.
Disable reverse DNS lookup in SSH:
SSHdconfiguration file using a text editor.
$ sudo vi /etc/ssh/sshd_config [sudo] password for user:
UseDNSdirective and set the value to
Add the line if it doesn't already exist and remove the
# at the beginning of the line if exists.
$ sudo systemctl restart sshd
|Red Hat Enterprise Linux|
|SUSE Linux Enterprise Server|