I need to connect two LANs with tunnel and give access to all devices. In each LAN there is MT router on the edge. Unfortunatelly, one of these Internet accesses is without public IP. I used to use IPSec to connect both LANs, but since there is no public IP, and it is changing from time to time, I am pretty sure it won't work this way. What would be the best way to securely enough connect these LANs?