Media Access Control

Creates and addresses the frame.

MAC Address

MAC-48 or EUI-48

MAC: Media Access Control
EUI: Extended Unique Identifier Example: 00-40-05-60-7D-49
No two NICs share MAC addresses. Always have to be unique.
Uses hexadecimal notation
48 bits total with 12 4 bit chars
- 48-bit binary address or 6-byte binary address
IEEE issues MAC address to manufacturer, referred to as OUI
- OUI: Organizationally Unique Identifier
NICs send a Layer 2 broadcast of FF-FF-FF-FF-FF-FF to request NICs MAC addresses. Every NIC on the network will process this.
When the MAC address isn't known a NIC can use the IP address (Layer 3) to request the MAC address of the target NIC.

Run these in terminal to see MAC addresses: Linux: ip a Windows: ipconfig /all MacOS: ifconfig