more network behind a specific router

[giulitn]

Hi all,
I have a NOKIA IP clsuter of two IP 3500 with CP NG R55.
I have to connect to tha corporate networks that lie behind the same private router that is not the default gateway of my LAN.
I have defined a specific NIC as internal on the same subnet of that router, with the topology not defined by IP & NETMASK but with a group of all subnets previously mentioned.

They can ping or telnet from the router but not from the other networks behind the router; the tracker show address spoofing even if it is disabled on the NIC; should I add that networks to my VPN doman of the cluster too?

Thanks