SSH is slow to make a connection

Question

I just installed Ubuntu 11.10, and whenever I try to SSH into my servers it's very slow. Before it displays the password prompt, it can take between 40 seconds and 60 seconds.

I use:

ssh myuser@myserver.com

Once I'm logged in, everything is fine and it works fast.

Why does it take so long, and how can i fix it? Are there any options in the SSH command I can use?

Answer 1

This is slow because the OpenSSH daemon uses DNS to run a reverse lookup on the client hostname to make sure it's valid

sudo vi /etc/ssh/ssh_config

Comment out the following lines

#GSSAPIAuthentication yes
#GSSAPIDelegateCredentials no

OR

add this:

UseDNS no