Cisco 1721 NAT and Nortel Extranet

[jabIsOnTheJob]

I've looked around these forums and seen a variety of opinions on whether or not it is possible for Nortel Extranet clients to form a VPN connection through a Cisco NATing router. In my case a Cisco 1721.

Is it possible? Is it possible for more that one client (using port forwarding). If so, does anybody have any clues they can pass on to me?

Thank you.