Switches (Layer 2) vs. Routers (Layer 3), MAC Addresses, ARP & VLANs
Why does every computer have both a MAC Address and an IP Address? And what is the exact difference between a Switch and a Router?
Run the 3 interactive flows below and watch the Live L2/L3 Envelope Inspector inside the diagram!
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The Envelope-Inside-an-Envelope Analogy:
The Layer-3 IP Header is the permanent ink letter addressed from Sender City/Street (Src IP) to Final Destination City/Street (Dst IP)—it stays the same for the whole trip.
The Layer-2 MAC Header is the outer courier pouch that only says "Which device in this room holds the packet next?"
A Switch reads the outer MAC pouch inside one room. A Router opens the outer MAC pouch, reads the inner IP address, and puts on a brand-new MAC pouch for the next room!