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What is a MAC Address?

/mæk/ Address

A MAC address, short for Media Access Control address, is a unique identifier assigned to network interfaces for communications on a physical network. It is a hardware address that is permanently programmed into the network interface during manufacturing.

OK, nerd…what does that mean?

Well…some guy…or gal named Hannas Anarion on Reddit, explains it this way…

It’s a unique device address given to each piece of network connected hardware. It’s different from an IP address because it’s permanent: every device has one and only one MAC address, but it is given a new IP address every time it connects.

Simply put, a MAC address is a unique identifier for a network device, that is embedded in the hardware of the device.

MAC addresses play a crucial role in the functioning of Ethernet and Wi-Fi networks. They are used to uniquely identify devices on a local network. When data is sent over a network, it is encapsulated in frames, and each frame contains the source and destination MAC addresses. This allows devices on the network to identify the intended recipient of the data.

A MAC address is a 48-bit number and is typically represented as six pairs of hexadecimal digits separated by colons or hyphens. For example, a MAC address might look like this: 00:1A:2B:3C:4D:5E.

A MAC address consists of 48 bits, which allows for a total of 2^48 (or 281,474,976,710,656) possible unique MAC addresses.


  • Two hundred eighty-one trillion,
  • four hundred seventy-four billion,
  • nine hundred seventy-six million,
  • seven hundred ten thousand,
  • six hundred
  • fifty-six

This large number of possible addresses ensures that the likelihood of two devices having the same MAC address is extremely low.

The first half of the MAC address (24 bits) usually identifies the manufacturer of the network interface card, while the second half (24 bits) is a unique identifier assigned by the manufacturer. That picture above is from a great article that includes an in-depth explanation of MAC addresses.

MAC addresses do not necessarily have to be entirely unique as manufacturers may reuse them, sometimes even unintentionally. Total uniqueness of MAC addresses for every device on the internet is not crucial. Instead, the numbers only need to be unique within a local network. If your laptop and my laptop share the same MAC address, they will function properly until both devices connect to the same Wi-Fi hotspot, which constitutes the same local network. In such a scenario, the operating systems on our laptops can assign new MAC addresses to avoid any collision or conflicts.

What about security?

It’s important to note that a MAC address operates at the data link layer of the network protocol stack and is only relevant within a local network. It is not routable across different networks, as routers typically strip off the MAC addresses and replace them with new ones when forwarding packets between networks. It’s a good system, but you know the saying, “With great power, comes great resp…” (I can’t afford to post the entire quote).

Take Spoofing as an example…MAC spoofing refers to the act of changing or impersonating the MAC address of a network device. It involves modifying the MAC address in its network interface settings, to make it appear as if it belongs to a different device.

By spoofing the MAC address, a device can masquerade as another device on a network, allowing it to bypass certain security measures or gain unauthorized access. It can be used for various purposes, both legitimate and malicious.

Legitimate uses of MAC spoofing include network testing, troubleshooting, and privacy protection. Network administrators may use MAC spoofing to simulate different network configurations or to test the functionality of network devices.

However, MAC spoofing can also be employed for malicious activities. An attacker may spoof a MAC address to bypass MAC-based filtering or access controls implemented on a network. This can be used to perform unauthorized activities or disguise the true identity of a device on a network.

It’s important to note that MAC spoofing operates at the local network level and does not allow an attacker to bypass network-level security measures such as firewalls or encryption. It primarily affects the identification and filtering of devices within the same local network.

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