Quiz Entry - updated: 2026.07.14
What are Layer 2 addresses and how do they differ from Layer 3 addresses?
Layer 2 (physical/MAC) addresses handle local delivery on a single link and change at every hop; Layer 3 addresses handle end-to-end delivery and stay the same the whole way.
Layer 2 addresses (also called physical addresses or MAC addresses):
* The Layer 2 MAC address is rewritten at every hop; the Layer 3 IP addresses stay constant end to end. *
| Characteristic | Layer 2 Address | Layer 3 Address |
|---|---|---|
| Purpose | Local delivery of frame on the link | End-to-end delivery across networks |
| Location | Frame header | Packet header |
| Scope | Used only on the local link | Used for routing between networks |
| Changes | Updated by each device that forwards the frame | Remains the same from source to destination |
Key insight: As a frame travels through a network, the Layer 2 addresses change at each hop (router), but the Layer 3 addresses stay constant.
Go deeper:
Packet Traveling — OSI Model & Encapsulation (Practical Networking) — animation showing MAC addresses rewritten hop-by-hop (local delivery) while the IP header stays end-to-end unchanged.- MAC address (Wikipedia) — defines the L2/MAC address in the data-link sublayer.