What are the two types of addresses used when sending data on an Ethernet LAN, and what is each used for?
A Layer 2 MAC (physical) address delivers the frame NIC-to-NIC on the same network; a Layer 3 IP (logical) address carries the packet end-to-end from source device to final destination.
Two primary addresses on an Ethernet LAN:
| Address Type | Layer | Purpose |
|---|---|---|
| Layer 2 Physical Address (MAC) | Data Link | Used for NIC-to-NIC communications on the same Ethernet network |
| Layer 3 Logical Address (IP) | Network | Used to send the packet from source device to destination device |
Key insight: Layer 2 addresses deliver frames locally; Layer 3 addresses enable end-to-end packet delivery across networks.
Context: When sending data, both addresses are needed - the IP address identifies the final destination, while the MAC address identifies the next hop on the local network segment.
Go deeper:
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Address Resolution Protocol (ARP) — PracticalNetworking on why Layer 3 IP (end-to-end) and Layer 2 MAC (hop-to-hop) addressing are two distinct schemes that must be bridged. -
MAC address — what a Layer 2 physical address actually is: a 48-bit NIC identifier, flat and only meaningful on the local segment.