Fix slow connections to Ubuntu SSH servers

As of Ubuntu 8.10 and older, connections to SSH servers with default configs can be annoyingly slow. This is because the OpenSSH daemon uses DNS to run a reverse lookup on the client to be sure that they aren’t faking their hostname. You can disable most look-ups by implementing the following setting:

As root edit “/etc/ssh/sshd_config” and add the line “UseDNS no“.

This can also be done by running the following command:

sudo echo "UseDNS no" >> /etc/ssh/sshd_config

Sources:

This issue is documented at OpenSSH.org

Fix and more details available at: http://tech.waltco.biz/2008/02/02/ssh-slow-to-connect-in-ubuntu-710-gutsy-gibbon/