Mac Address

What is Mac Address

A MAC Address (Media Access Control Address) is a unique identifier associated with a network interface of a device, such as a laptop, smartphone, router, or network card. It is also know as Physical Address.

MAC Addresses are unique 48-bit hardware numbers of a computer that are embedded into a network card (known as a NIC) during manufacturing.

MAC addresses are mainly used for communication within a local network (LAN). They operate at Layer 2 (Data Link Layer) of the OSI model.

Format of Mac Address

A MAC address is commonly a 48-bit (6-byte) address written using 12 hexadecimal characters.

A typical MAC address looks like this:

00:1A:2B:3C:4D:5E

It is divided into six groups, with each group containing two hexadecimal digits.

00 :  1A :  2B :  3C :  4D :  5E
│     │     │     │     │     │
2     2     2     2     2     2
hex   hex   hex   hex   hex   hex
digits digits digits digits digits digits

Common MAC Address Formats

Colon-separated:

00:1A:2B:3C:4D:5E

Hyphen-separated:

00-1A-2B-3C-4D-5E

Dot-separated:

001A.2B3C.4D5E

What Does Each Part of a MAC Address Identify?

A traditional 48-bit MAC address is commonly divided into two main parts:

00:1A:2B : 3C:4D:5E
─────────   ─────────
First 24    Last 24
bits        bits

1. First 24 Bits — OUI

The first 24 bits (3 bytes) are commonly called the OUI (Organizationally Unique Identifier). It is a value used to identify an organization that has been assigned a block of MAC addresses.

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For example, an organization may receive a MAC address block and then assign individual addresses from that block to network interfaces.

Last 24 Bits — Device/Interface Identifier

The remaining 24 bits (3 bytes) are used to distinguish network interfaces within the assigned address space. In traditional globally administered MAC addresses, this part is assigned by the organization to individual network interfaces.

Types of MAC Address

1. Unicast MAC Address

A Unicast MAC Address is a MAC address used to identify one specific network interface on a local network.

When a device sends an Ethernet frame to a unicast MAC address, the frame is intended for one specific destination device/interface.

2. Multicast MAC Address

A Multicast MAC Address is a MAC address used to send an Ethernet frame to a group of network interfaces instead of just one device.

In multicast communication, the sender sends one copy of the data, and multiple devices that belong to the multicast group can receive it.

3. Broadcast MAC Address

A Broadcast MAC Address is a special MAC address used to send an Ethernet frame to all devices on the local Layer 2 network segment.

The Ethernet broadcast MAC address is:

FF:FF:FF:FF:FF:FF

When a device sends a frame with this destination MAC address, the frame is intended for every device on the same local broadcast domain.