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Thank you for asking this question in the support community. I'm not familiar with the Linksys RV082 router, but here are some general guidelines for connecting another vendor's router to an ADTRAN router provided by the ISP.
First, when connecting two routers directly to each other an Ethernet crossover cable is needed. If there is a switch between the two routers, then an Ethernet straight-through (patch cable) can be used. Typically, the ISP router's port that is facing the customer (inside) will be assigned a public IP address and subnet block. You will need to assign the port on your router (public) that connects to the ISP's router to be an address in that same public IP address subnet. Then the default-route or default-gateway of your router will need to point to the IP address of the directly connected ISP router's interface. In your scenario, the Linksys router will need to perform network address translation (NAT), and there will be no configuration changes necessary for the ISP's router.
In summary, connect the routers with the appropriate cable, assign your router with an IP address in the same subnet as the ISP's router, point the default route of your router to the IP address of the ISP's router in the same subnet, and configure your router to perform NAT.
I hope that makes sense, but let me know if you have any further questions.
Levi
