What is MAC address: Format and Types

MAC address is formed according to principles of two numbering spaces that are based on extended unique identified (EUIs) that are managed by IEEE.

In this article on what is MAC address, we will be discussing the format and types of this physical address in detail.

Table of Contents

• What is MAC address?
• MAC address Format
• What is MAC Cloning?
• Use of MAC in Hosts
• Requirement
• Why do We Need Both MAC and IP addresses?
• Types
• Finding MAC address
• Difference Between MAC Address and IP Address

What is MAC address?

To understand what is MAC address, let us first understand the definition of this physical address. MAC address full form is Media Access Control address. Unlike IP address, it is a unique identifier that is assigned to the network interface controller (NIC). This is used as a network address in communications within the network segment. There are three more ways to refer MAC address: hardware address, physical address, and Burned In address (BIA). For any device, there is a unique address, and no two devices can ever have the same MAC address. It works on the data link layer of an OSI model. 

The vendor of the device provides this address at the time of manufacturing and is embedded in NIC. Due to this reason, it cannot be changed. MAC works on layer 2 of the OSI model and helps in identifying devices that are within the same broadcast network. There can be three representations of MAC address, including the following:

• Hyphen-Hexadecimal notation 00-0a-95-9d-67-16
• Colon-Hexadecimal notation 00:0a:95:9d:67:16
• Period-separated hexadecimal notation 000.a95.9d6.716

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MAC Address Format

The format of the MAC address is hexadecimal. Let us understand this with a sample address:

00:0a:95:9d:67:16

There are twelve numero-alpha digits in a MAC address that are 48-bit long. The first 24 bits represent Organizational Unique Identifier and the remaining 24 bits are either for NIC or are vendor specific.

The first three octets are used as Organisationally Unique Identifier. The IEEE Registration Authority Committee assigns these MAC prefixes. The last three octets are specific to NIC and are used by manufacturer for every NIC cards. Vendors can use any sequence of digits to NIC-specific digits. In this case, the prefix must be the same as provided by IEEE. 

What is MAC Cloning?

MAC cloning is a networking technique where you copy or "clone" the MAC address of one network device to another. It is the process of changing a network interface's MAC address to match another device's MAC address. This can be done for various reasons:

1. Network Access Control Bypass

• Some networks restrict access based on registered MAC addresses
• By cloning an approved device's MAC address, a new device can gain network access

2. Internet Service Provider (ISP) Authentication

• Some ISPs bind internet service to a specific MAC address
• MAC cloning allows users to transfer service to a different device or router

3. Privacy and Anonymity

• Changing the MAC address can help mask the original device's identity
• Useful in scenarios where you want to prevent device tracking

How MAC Cloning Works

• The device's network interface software manually sets the MAC address to match another device
• Most modern routers and network interfaces support MAC address modification
• The cloned MAC address replaces the original hardware-assigned MAC address

Use of MAC in Hosts

The MAC (Media Access Control) address has a crucial role in network communication for hosts.

1. Unique Device Identification:

• Every network interface has a unique MAC address
• Allows for precise identification of devices on a network

2. Layer 2 Communication:

• Used in the data link layer of the OSI model
• Enables direct communication between devices on the same local network

3. Address Resolution:

• Crucial for ARP (Address Resolution Protocol)
• Maps IP addresses to MAC addresses for local network routing

4. Network Access Control:

• Used in MAC address filtering for basic network security
• Can restrict network access to devices with approved MAC addresses

5. DHCP Operations:

• Helps in IP address assignment by DHCP servers
• Can be used to ensure consistent IP assignment for specific devices

6. Network Troubleshooting:

• Assists in identifying specific devices during network diagnostics
• Useful for tracking network traffic and resolving connectivity issues

7. Network Switching:

• Switches use MAC addresses to forward frames to the correct port
• Enables efficient local network traffic management

8. Virtual LAN (VLAN) Configuration:

• Can be used in VLAN assignments in some network setups
• Helps in logical network segmentation

9. Wake-on-LAN Functionality:

• Allows remote wake-up of devices using their MAC address
• Useful for network management and power saving

10. Device Tracking and Management:

• Facilitates inventory management of network-connected devices
• Useful for IT asset tracking in large organizations

Requirement for Unique MAC Address

It is important for the system to have a unique address in LAN network since LAN with same MAC address will prevent the network from working. Let us understand this with an example. Suppose X, Y and Z are connected through switch. Their respective addresses are 11000ABB28FC, 00000ABB28FC and 00000ABB28FC. 

Here NIC of devices Y and Z have the same address. In case, device X sends data frame to 11000ABB28FC, the switch will be unable to deliver the frame to the destination since two destinations have the same MAC address.

Types of MAC Addresses

The following are the three main types of MAC addresses:

1. Unicast MAC Address

To identify whether an address is Unicast, it is important to consider the first byte. The first byte has 8-bits (b7, b6, b5, b4, b3, b2, b1, b0). Here, b7 is the Most Significant Bit (MSB) whereas b0 is the Least Significant Bit (LSB). When LSB is 0, it is a unicast address. Let us consider an example to understand the unicast address. 

Suppose the MAC address is 4A:30:10:19:10:1A. Here, the first byte is 4A which is in hexadecimal. A has the decimal value of 10. Since the hexadecimal value is base 16, we have value ranging from 0 to 15, where 15 represents F in hexadecimal. Let us now, use a pattern noted as 8 4 2 1 since on summing these up, we get the value 15. Now, we will pick 4A, the target; and now we will split it into 4 and A. 

From 8 4 2 1 pattern, locate 4 and place 1 under it  (turning it on). By placing zero, we are turning off the rest. This will result in 0100. Since A is 10, we need to seek combinations that will result in 10. For this, we have 8 and 2, which will turn on and put the rest OFF. This will result in 1010. Now, we will join these binary values that will result in 0100 1010. Since this ends with zero, it is a unicast address.  

2. Multicast MAC address

It is a type of address that enables source device to transmit data frames to multiple devices or NICs. In the layer 2 Multicast address, LSB or the first 3 bytes of first octet of an address is set to be one and reserved for multicast addresses. The remaining 24 bits are used by devices that want to send data in a group. A multicast address startes with 01-00-5E as prefix. If LSB is 1, it is a multicast address. Let us consider 01:00:5E:00:01:01. Here, 01 will result in 0000 0001. Since it ends with 1, it is a multicast address.

3. Broadcast MAC address

This address represents every device within the network. Ethernet frames with ones in all bits of destination address are known as broadcast address. These bits are reserved addresses for broadcast. Frames destined with MAC address FF-FF-FF-FF-FF-FF reach every computer belonging to that LAN segment. In case, a source device wants to send data to every device within a network, it can use the broadcast address as the destination address. 

Why Do We Need Both MAC and IP Addresses?

MAC and IP address are required for the following reasons:

• Different Layers Use Them: MAC addresses are used within a small area like your home network. IP addresses are used for sending data over the internet to far places.

• Type of Addressing: MAC addresses come with your device and don't change. IP addresses are like temporary tags given to your device when it connects to a network.

• Local vs. Worldwide: MAC addresses help send information to the right device nearby. IP addresses help send information to the right place over the internet.

• Working Together: Both addresses help devices talk to each other. MAC addresses focus on the immediate area, while IP addresses focus on reaching far away places.

• Moving Around: Your device's IP address can change if you go to a new place, like a different coffee shop. But the MAC address stays the same.

• Building Networks: IP addresses help organize the internet so data knows where to go. MAC addresses make sure the data gets to the right device close by.

• Keeping Things Safe and Organized: MAC addresses can help keep unwanted devices off your home network. IP addresses help manage where data should go and keep an eye on network traffic for safety.

Finding MAC Address

To find this address for a laptop, one of the three ways must be followed according to the version of the your laptop. 

For Windows laptop

1. Press the Windows+R key. Now, type ncpa.cpl and press enter. Then right click on Wifi or Local area connection and select status. Click on Details to find the address. 
2. Search for cmd.exe on your computer. On the black Command Prompt screen, you need to type getmac /v. This will list down adapters. The physical address is your MAC address.

Apple OS

1. First of all, select System Preferences from Apple menu present at the top left of your screen. Then click on Network from System Preferences Menu. Choose Wi-Fi from the list of interfaces present on left and click on the Advanced button. Now, choose the hardware tab to view the MAC address of the wireless card.

Linux 10.10.X and above

Right click on network arrow and select the option of Edit connections. Click on the Ethernet adapter till it is orange and then select ‘Edit’. This will show the MAC address. 

On smart devices

• Apple iOS: You need to tap on settings and then on general. Now tap on About and scroll down to Wi-Fi address.
• Phone(Android): Tap on the menu button on the home screen and then go to settings. Tap on About Phone and then, tap on status or hardware information. Scroll down to find the Wi-Fi MAC address. 
• Tablet (Android): Press on Menu Key and go to settings. Scroll down and tap on About Tablet and tap on Hardware Info or Wi-Fi settings. Then scroll down to view the Wi-Fi MAC address. 

Difference Between MAC Address and IP Address

The following explains the difference between MAC and IP address