Let’s say my device wants to send a packet to far way device many networks away. Once my router receives the packet, it doesn’t know much about this destination IP and chooses to send it to the next hop router. Our router is connected to 100s of routers. My question is how does the network layer pass down the information of which of the available next hops for data link layer to encapsulate the packet with. ie, how does the DLL get to know about the routing decision NL made so that it can do its encapsulation with destination mac. Because it doesn’t get to know anything from reading the final destination IP. it needs to know the next hop IP. (Assume that the DLL already knows the mac of the next hop router).
Is this a wrong way to think about routers, because they also have the ability to step into transport layer and change the port number can they also interfere in the DLL and do all operations by itself in reality?
