The 3002 can only have one network behind it, or I should say, will only advertise one network to the head-end concentrator.
The easiest way to do this is enable NAT/PAT on the router separating the two internal networks, so that when traffic from the 2nd network comes through the router, it gets changed to a source address of the 1st network. On the way back traffic gets sent back to the router and gets NAT/PAT'd back to the original address.