sshd
To disable reverse DNS lookup in sshd:
If network connectivity is working appropriately (you can ping the box without any problem), but if it takes a long time to log into your server, chance is that your sshd is doing reverse DNS lookup. If you only access this server from trusted / private network, you can disable reverse DNS lookup by editing /etc/ssh/sshd_config to contain:
UseDNS no
page revision: 1, last edited: 03 Jun 2010 17:59