What is MAC (Media Access Control) Address?

Introduction

A MAC address, also known as a Media Access Control address, is an identifier given to a network interface controller (NIC) in a device that communicates through a network. They have uses, including filtering, routing, security, and identifying devices. In this blog, we will explain the MAC address and its purpose. We will also discuss its different types available and how to find MAC address on different devices or OS.

Before getting into more details, let’s first understand what a MAC address really is.

What is MAC Address?

A MAC address, also known as a Media Access Control Address, serves as an identifier assigned to a network interface controller (NIC). It is mainly for communication purposes within a network segment. An NIC is a hardware component that enables device connectivity to networks like Ethernet, Wi-Fi, or Bluetooth.

Format of MAC Address

A MAC address is typically represented by 12 hexadecimal digits (0-9 and A-F) separated by colons or dashes. For instance, 00:0A:95:9D:67:16 or 00-0A-95-9D-67-16. Each hexadecimal digit represents four bits, and every pair of digits signifies one byte or octet. The initial six digits in a MAC address indicate the NIC manufacturers, known as Organizationally Unique Identifier (OUI), while the remaining six digits are assigned by the manufacturer to identify the NIC. In the given example, 00:0A:95:9D:67:16, the OUI 00:0A:95 belongs to Hewlett Packard Company, and the NIC-specific part is 9D:67:16.

Now that we have a basic understanding of the Media Access Control address, let’s discuss its purpose.

Purpose of MAC Address

The primary purpose of a MAC address is to ensure that each device that is part of the network has its distinct and unchanging identification method. Unlike IP addresses, these addresses are typically permanent and pre-programmed into the network interface card (NIC) by the manufacturer. This implies that even if a device alters its IP address or switches networks, its MAC address remains unchanged.

These addresses are utilized by protocols within the data link layer of the OSI model. This layer is responsible for facilitating data transfer between neighboring nodes on a network. One such protocol is the Address Resolution Protocol (ARP), which maps IP addresses to MAC addresses. When a device intends to communicate with another device on the network segment, it needs to know the Media Access Control address of that device.

To obtain this information, the device sends an ARP request broadcasting the IP address of the desired destination and requesting its corresponding MAC address. The device with a matching IP address responds with an ARP reply providing its Media Access Control address. The sender then stores this information in its ARP cache for reference.

Another protocol that relies on it is Ethernet, which serves as the used standard for networks. Ethernet frames act as units of data transmitted over an Ethernet network. Each Ethernet frame includes a header containing both source and destination MAC addresses and details such as frame type and length. The source address identifies the sending device, while the destination address specifies which device should receive it.

The Ethernet switch or hub is in charge of connecting the devices within a network segment and utilizes these addresses to direct the frames to their ports. Learn the difference between Hub and Switch.

Types of MAC Addresses

There are three types of MAC addresses: unicast, multicast, and broadcast.

Unicast

A unicast MAC address is used to identify a single device within a network. It is also referred to as a globally unique address. It can be distinguished by having the least significant bit (LSB) of the first octet set to 0. For instance, 00:0A:95:9D:67:16 is an example of a unicast address because its first octet is 00, and the LSB is 0.

The OUI portion of this address can be further classified into two categories: universally administered addresses (UAA) and locally administered addresses (LAA).

The manufacturer of the NIC assigns a UAA and adheres to IEEE standards for OUI allocation. On the other hand, an LAA is assigned by the network administrator that does not follow any specific standards for OUI allocation. An LAA can be identified by having its second least significant bit (SLSB) of the first octet set to 1. For example, 02:0A:95:9D:67:16 represents an LAA because its first octet is 02 (00000010), and the SLSB is 1.

Multicast

A multicast MAC address is used to identify a group of devices on a network that share a common interest or function. It is also known as a group address. In a multicast address, the LSB of the first octet is set to 1. For instance, if we take the example 01:0A:95:9D:67:16, it qualifies as a multicast Media Access Control address because its first octet is 01 and its LSB is 1.

Broadcast

A broadcast MAC address is mainly used to identify all devices within a network segment. It is also referred to as a universal address. In a broadcast address, all bits are set to 1. For instance, if we consider FF:FF:FF:FF:FF:FF as an example, it represents a broadcast address since all its bits are set to 1.

The purpose of using a broadcast Media Access Control address is to send frames to all devices within the network segment without considering their individual MAC addresses. For example, an ARP request utilizes a broadcast address as its destination address in order to reach all devices within the network segment. Here are the difference between Broadcast and Multicast.

Difference between MAC Address and IP Address

Here are some differences between MAC and IP Address –

Reasons to have both IP and MAC Address

Especially in the structure of the OSI model, the reason for having both MAC and IP addresses depends on the way the Internet works. How the data is sent and received over a network is described by the OSI model also known as a conceptual framework. It is divided into seven layers and each of these layers performs specific functions.

• Layer 2 is responsible for packet delivery from hop to hop and it uses MAC addresses.
• Layer 3 is responsible for packet delivery from end to end and uses IP addresses.

A MAC (Media Access Control) address is used in Layer 2 (Data Link Layer). These are unique numbers that are linked to network interfaces to facilitate data link layer communication.

Media Access Control addresses’ primary function is to manage how data is transported from one network node to another on a direct, physical basis – this is also known as “hop to hop” delivery.

Nonetheless, an IP (Internet Protocol) address is used by Layer 3 (Network Layer). Devices on a network are identified by their IP addresses, which are also used to route data between networks. IP addresses guarantee that data travels from its original source to its destination; this process is known as “end-to-end” data transmission.

An IP header, which contains the source and destination IP addresses, is first sent with data by a computer. The source and destination MAC addresses for the current “hop” in the path are included in the MAC header, which encapsulates the data and the IP header.

The MAC address header is removed, and a new one is created for the next hop as data moves from one router to the next. But until it gets to its destination, the IP header—which was created by the original computer—remains intact.

This procedure demonstrates the way the MAC headers handle the “hop to hop” delivery and the IP header controls the “end to end” delivery.

Therefore, IP addresses and MAC addresses are both necessary for the Internet to work. IP addresses guarantee that the data reaches its intended destination, whereas Media Access Control addresses enable the direct, physical transfer of data between network nodes.

Characteristics of MAC Address

Here are the major characteristics of a Media Access Control address:

• These are unique addresses that help identify devices and enable communication between networks.
• It is coded into the hardware of the device’s network interface card (NIC) which remains unchanged but, in some cases, the manufacturer provides specific tools for change.
• The first 3 bytes show the maker ID, and the last 3 bytes show a unique identifier allocated by the maker.
• These are associated with the Address Resolution Protocol (ARP) to create communication between IP addresses and MAC addresses over a LAN.
• Operating systems like Windows and Linux provide access to your network adapter’s Media Access Control address through the command prompt or network settings.

Advantages of MAC Address

Some of the advantages are:

• There is no hassle to configure and manage these addresses and no additional network infrastructure is required.
• The use and support of multiple networking technologies and protocols make MAC addresses naturally compatible with many devices.
• The uniqueness of these addresses helps to easily identify and maintain devices throughout the network.
• Only devices with authentic Media Access Control addresses are connected, thereby limiting access to the network.
• Network problems can be resolved by analyzing the root cause of the problems and monitoring network activity.
• These addresses help in multicasting to send the same packet to multiple devices simultaneously.
• Identifying and communicating with each other quickly and easily helps in efficient communication over the network.
• Direct communication of devices without additional routing or addressing helps reduce network overhead.
• Many network configurations and topologies (including client-server, peer-to-peer, and hybrid models) are supported by MAC addresses.

Disadvantages of MAC Address

Some of the disadvantages are:

• MAC addresses are 48-bit numbers i.e. there is a limited number of possible these addresses. This can be harmful when many devices have the same Media Access Control address.
• These can be compromised by enabling unauthenticated devices to view the network.
• Since, these are not organized systematically, large networks are difficult to manage efficiently.
• At the time of manufacturing, thes are allocated that cannot be easily changed and devices cannot be reconfigured or replaced which can be a limitation in those situations.
• These Addresses are not allowed to identify devices outside the local network as they are only allowed to identify devices within the local network.
• Media Access Control addresses are integrated with the device’s network interface card (NIC), which means that a NIC failure affects it as well.
• While sharing a MAC address, the text format is simple which can be dangerous.
• Media Access Control addresses themselves have no default security features, instead MAC filtering allows access to the network to be restricted.
• The probability of its collision is very low, but if a collision occurs it disrupts the network and thus it is hard to recognize and maintain devices over the network.

Now, many of the students or enthusiasts have a keen interest in finding the MAC address of a device. But how to find it? Below, we have explained the whole process on various devices in easy steps.

How to find MAC Address of a Device?

Here are different ways of finding Media Access Control address of various devices –

Windows

Here is how you can locate the MAC address on Windows:

• Begin by opening the Command Prompt. You can do this by either typing “cmd” in the search box or pressing Windows+R followed by typing “cmd” and hitting Enter.
• Once the Command Prompt opens, type “ipconfig/all”, and after that, Press Enter.
• Locate the Physical Address field under either the Ethernet adapter or Wireless LAN adapter section. This will display your device’s MAC address.

Mac OS

To locate the MAC address on Mac OS, one can follow the below steps:

• Click on the Apple icon, open the Apple Menu and go to System Preferences.
• Within the System Preferences, choose Network.
• This will open a network window where you can select the Wi-Fi option.
• In this section, you will find the MAC address displayed under Wi-Fi or Ethernet addresses.

Linux

Here’s a step-by-step guide to locating the MAC address on Linux:

• Start by opening the Terminal. You can do this by pressing Ctrl+Alt+T or searching for “Terminal” in your applications menu.
• Type in “ifconfig -a”, and after that, Hit Enter.
• Look for the HWaddr field under either the eth0 or wlan0 section. This field displays the MAC address of your device.

Frequently Asked Questions

Q1. What is MAC address and IP address?

A MAC address serves as an identification for a network device like a router or computer. On the other hand, an IP address is a label that helps identify devices on networks such as the Internet or local area networks.

Q2. How to find a MAC address?

Finding a MAC address is different in different machines or OS. For example, in the case of Windows, one can find the MAC address by typing ipconfig/all in the CMD. For Linux, one can find it by typing ifconfig -a in the terminal.

Q3. What are the 3 types of MAC address?

The three types of MAC addresses are:

• Unicast MAC address
• Multicast MAC address
• Broadcast MAC address

Q4. What is the full form of MAC?

The full form of MAC is Media Access Control.

Conclusion

In this blog post, we’ve covered all the crucial concepts of MAC addresses in networking. We discussed what it is, its purpose, structure, and types. Apart from that, we also explained how to find it on a device and shared some facts about MAC addresses. We hope this information has helped you gain an understanding of these addresses and their significance in networking.

MAC Address is an essential part of CCNA Training. If you want to learn more about it, you should check out PyNet Labs’ CCNA Course. If you have already completed with the CCNA Training, you should check out CCNP ENCOR Training to advance your knowledge.