Let router A connects two LANs L1 and L2 into an internetwork, and router B connects two LANs L3 and L4 into an internetwork.
Can the two internetworks be connected into an internetwork?
Is it done by connecting router A and B?
If yes, is the connection between A and B treated the same as an connection between A and LAN L1?
Let me clarify my last question. I assume routers A and B are just gateways between networks for internetworking, without having non-gateway features that are commonly added to personal routers. I am not familiar with gateway only routers, except reading a little on Tanenbaum's Computer Network book. But my last question comes from a comparison to personal routers. In my apartment, my personal router has a WAN port and several LAN ports. Back to the case here, do routers A and B (as gateways only) have different ports similarly? What ports of routers A and B are used to connect between A (or B) and the LANs and to connect between A and B?