- 48-bit flat address that is locally unique
- Used locally to get frame from one interface to another physically-connected interface (inside the same network)
- Used at Link Layer level
- Manufacturer buys portion of MAC address space to assure uniqueness
- Burned in NIC ROM, sometimes can be set in software
MAC Addresses vs IP Addresses
IP Addresses are used for communicating between networks, MAC addresses are used for communicating between machines within same network
Analogy:
- MAC addresses are like SSNs (shows identity, unique), whereas IP address are like postal addresses (can be changed)
MAC addresses’ flat nature provides portability
- Can move LAN card from one LAN to another
- IP’s hierarchical address not portable
- Address depends on IP subnet to which node is attached