Many of you must have faced slow ssh auth in Ubuntu or any other linux client. To eliminate delay you may change following in /etc/ssh/ssh_config.
from #GSSAPIAuthentication yes
to #GSSAPIAuthentication no
GSSAPI (Generic Security Service Application Programming Interface) is a function interface that provides security services for applications in a mechanism-independent way. This allows different security mechanisms to be used via one standardized API. GSSAPI is often linked with Kerberos, which is the most common mechanism of GSSAPI.
Refer
