Dual Firewall with ISA Please Help

So i’ve got 2 sonicwall devices that tunnel to eachother… There are 2 networks, one being the SBS network, 192.168.16.x and the remote network 192.168.17.x I would like to have 192.168.17.x communicate with the 192.168.16.x interface on the “Trusted” side of ISA. So far i can get the 192.168.17.x interface to ping the outside interface of ISA which is 10.0.0.2 Any ideas on how to get the vpn traffic through ISA?