Choosing which interface to use

[hal]

I am setting up a VPN client on a 6.0 box of mine.
As a result of the VPN client (openvpn) running I
have two interfaces active, xl0 needed by the dhcp
client and tun0 used by the vpn client.

The question.  How do I tell an application perhaps telnet,
ssh, or ftp to use tun0 and not xl0?

hal