SSH Login Slow — Removing Delay

Problem: When I’m trying to log into the remote server via SSH, after I enter the UserName, it takes a lot of time before it displays the Password prompt. How to solve this problem?

Solution: Basically, a long delay during authentication process is caused by “GSS API Authentication method” or/and by “UseDNS” option. The solution is to disable the GSSAPIAuthentication method and to set the UseDNS to “no” on the SSH Server.

Edit SSH Server configuration file:

# vi /etc/ssh/sshd_config

UseDNS: Specifies whether sshd 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”.

Set the UseDNS to “no” as shown below:

UseDNS no

GSSAPIAuthentication: Specifies whether user authentication based on GSSAPI is allowed. The default is “no”.

Set the GSSAPIAuthentication to “no”:

GSSAPIAuthentication no

Restart the OpenSSH server to apply changes

For Fedora/Centos/RHEL etc.:

# service sshd restart

For Debian/Ubuntu/LinuxMint etc.:

# sudo service ssh restart

Now you could connect to your Server with SSH quick as usual.