Speedup SSH Authentication
Did you wait like 10 seconds to ssh into another machine which is just within one feet ?, Well the problem seems to be ssh authentication requires a time consuming DNS lookup.
Fix for this problem is to disable DNS lookup during authentication. Follow steps below to fix this. Open up the file /etc/ssh/sshd_config file as root user and append the following line to it.
Save the file and exit the editor.Now restart ssh service by executing following command.
sudo /etc/init.d/ssh restart
From now on your ssh logins should work like a breeze.