I'm new to networking. And as far as I understand about ARP messages, Alice can only send ARP to Bob if two are connected. But if Alice and Bob are connected to a router, but not connected to each other, they can't send ARP to each other right? Or is there any other day way that Alice can send ARP packets to Bob through the router?
ARP is Layer 2 Protocol. It is not working on Router. Because Router is working on Layer 3. If Bob and alice connected through router,then they looking at IP address.
If Bob and Alice connect to switch, Then ARP come to action. Then they looking at ARP table and forward traffic based on MAC address which is related to IP address.