MAC Address
A MAC (Media Access Control) address is the physical address written into every network interface by its manufacturer. An IP address is assigned later and changes; a MAC address ships with the hardware.
01IP vs MAC
| Feature | IP address | MAC address |
|---|---|---|
| Changes? | Yes — network to network | No* |
| Assigned by | DHCP / admin | Manufacturer |
| Format | 192.168.1.1 | AA:BB:CC:DD:EE:FF |
| Layer | Layer 3 (Network) | Layer 2 (Data Link) |
| Scope | End to end | Local network only |
*It can be changed in software (MAC spoofing), but the hardware record is fixed.
The first half identifies the maker: AA:BB:CC is the vendor code (OUI), DD:EE:FF is the per-device serial. That's why you can look at a MAC address and say "that's an Apple card."
02How do the two work together?
When you send a packet, two questions get answered in order:
- IP address → which network should this go to?
- MAC address → which device inside that network gets it?
Courier analogy: IP finds the city and neighborhood, MAC delivers to the door. On the local network, the protocol that asks "who owns this IP's MAC?" is called ARP — and in later lessons you'll see how switches build tables of these addresses.
03Seeing your MAC address
| Operating system | Command |
|---|---|
| Windows | getmac or ipconfig /all |
| Mac | ifconfig (the ether line) |
| Linux | ip link show |
04Summary
- MAC = physical address burned into hardware, used for local delivery
- IP = logical address, used for travel between networks
- IP finds the city, MAC knocks on the door — they work as a pair