[CentOS] sshd won't bind to tun0

Hi all,
I have a strange situation.
I have a machine connected to an AT&T VPN.
Sometimes the VPN gets disconnected, so I create a cronjob to restart
the VPN client when it happens:
Problem is: sshd seem doesn't want to bind to tun0.
I restart ssh, network, no good.
Anyone has any clue? So strange.
Thank you.