MAC Address Explained: The Hardware Identity of a Device
A MAC address is a 48-bit hardware identifier burned into every network interface, written as six hex pairs like 00:1A:2B:3C:4D:5E. It operates at Layer 2 — switches forward frames using MAC addresses, while routers use IP addresses at Layer 3.
Format: OUI + device ID
The first 24 bits are the OUI (Organizationally Unique Identifier) — a vendor code assigned by the IEEE (so you can often tell the manufacturer). The last 24 bits uniquely identify the specific interface. Together they're meant to be globally unique.
MAC vs IP address
An IP address is logical and changeable (assigned by config or DHCP, used for routing between networks). A MAC address is physical and fixed (used for delivery within a single network). A packet keeps the same source/destination IP end to end, but its MAC addresses change at every hop. Understanding this split is fundamental to CCNA.
Frequently asked questions
What is a MAC address?
A 48-bit hardware address uniquely identifying a network interface, used by switches to forward frames at Layer 2.
What is the difference between a MAC and an IP address?
A MAC address is a fixed physical identifier used for local delivery (Layer 2); an IP address is a logical, changeable identifier used for routing between networks (Layer 3).
What is an OUI in a MAC address?
The first 24 bits — the Organizationally Unique Identifier — an IEEE-assigned vendor code that identifies the interface manufacturer.
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