MAC Addresses

Each host in a network has its own 48-bit (6 octets) Media Access Control (MAC) address, represented in hexadecimal format. MAC is the physical address for our network interfaces. There are several different standards for the MAC address:

• Ethernet (IEEE 802.3)
• Bluetooth (IEEE 802.15)
• WLAN (IEEE 802.11)

This is because the MAC address addresses the physical connection (network card, Bluetooth, or WLAN adapter) of a host. Each network card has its individual MAC address, which is configured once on the manufacturer's hardware side but can always be changed, at least temporarily.

Let's have a look at an example of such a MAC address:

MAC address:

• DE:AD:BE:EF:13:37
• DE-AD-BE-EF-13-37
• DEAD.BEEF.1337

When an IP packet is delivered, it must be addressed on layer 2 to the destination host's physical address or to the router / NAT, which is responsible for routing. Each packet has a sender address and a destination address.

The MAC address consists of a total of 6 bytes. The first half (3 bytes / 24 bit) is the so-called Organization Unique Identifier (OUI) defined by the Institute of Electrical and Electronics Engineers (IEEE) for the respective manufacturers.

The last half of the MAC address is called the Individual Address Part or Network Interface Controller (NIC), which the manufacturers assign. The manufacturer sets this bit sequence only once and thus ensures that the complete address is unique.