I had some ssh problems on my trixbox installations. Each time I try to connect to the trixbox using ssh I had some delay. The classical solution for this is to disable the reverse DNS lookups by changing the line in /etc/ssh/sshd_config to:

UseDNS no

But in this case, this didn't solve my problem. I ran my connection wth verbosity.

ssh -vvv some.host.com

I had a delay in this step:

debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure.  Minor code may provide more information
No credentials cache found
debug1: Unspecified GSS failure.  Minor code may provide more information
No credentials cache found
debug1: Unspecified GSS failure.  Minor code may provide more information

AFAIK, this is related to openssh kerberos authentication. This is something that I really really don't need. So I disabled in /etc/ssh/sshd_config the lines:

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPIAuthentication yes
#GSSAPICleanupCredentials yes
#GSSAPICleanupCredentials yes

After the restart, there was no delay. Even with the "UseDNS yes".