See Set Up SSH Keys.

ssh -v ...

Take care of both with this one-liner:

On the Client PC:

echo "Host *
        ServerAliveInterval 60
        GSSAPIAuthentication=no" >> $HOME/.ssh/config

(be sure to copy and paste everything including the CRLF's and spaces)

If a permissions error is thrown:

chmod 600 /home/gcooper/.ssh/config

Adjust your firewall first or you may lose access!

vim /etc/ssh/sshd_config

Port 2222

service sshd restart

http://www.alexonlinux.com/reverse-ssh-tunnel-or-connecting-to-computer-behind-nat-router

This technique is used to access an SSH host behind a NAT firewall.