Introduction:
In computer networking, a MAC (Media Access Control) address is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. Every device that connects to a network has a MAC address assigned to it. MAC addresses are used for numerous purposes in networking, including network address assignment, network device identification, and network security. It is an essential part of network communication, and understanding MAC addresses is crucial for troubleshooting and security purposes.
What is a MAC Address?
A MAC address is a unique identifier assigned to a network interface controller (NIC) by the manufacturer. It is used as a network address for communication within a network. MAC addresses are also known as physical addresses or hardware addresses or ethernet address.
Structure of MAC address:
A MAC address is a is a 48-bit (6-byte) address that consists of six pairs of hexadecimal numbers, separated by colons or hyphens. The first three pairs of digits identify the manufacturer of the device, while the remaining three pairs are assigned by the manufacturer to identify the specific device. Example of MAC address: 00-1B-44-11-3A-B7
How Does a MAC Address Work?
MAC addresses are used by the data link layer of the OSI model, which is responsible for transmitting data over a network. When a device wants to send data to another device on the same network, it includes the destination MAC address in the data packet. The data is then transmitted to device on the network until the device with the matching MAC address receives it.
It is important to note that MAC addresses only apply to communication within a local network segment. When data is transmitted between different network segments or over the internet, a different addressing scheme (such as IP addresses) is used.
How are MAC Addresses Assigned?
MAC addresses are assigned by the manufacturer of the device’s network interface controller. The first three bytes or three pairs of digits in a MAC address identify the manufacturer called the OUI (Organizationally Unique Identifier), and are assigned by the Institute of Electrical and Electronics Engineers (IEEE). The remaining three bytes or pairs are assigned by the manufacturer themselves.
MAC addresses can be viewed using a variety of tools, such as the command prompt on Windows or the terminal on macOS and Linux. They can also be changed, although doing so is generally not recommended as it can cause network communication issues.
Types of MAC Addresses:
There are three types of MAC addresses: unicast, multicast, and broadcast.
Unicast address:
A unicast MAC address is used to identify a specific device on the network. When a device wants to send data to another device, it sends it to the unicast MAC address of the destination device.
Multicast address:
A multicast MAC address is used to identify a group of devices on the network. When a device wants to send data to a group of devices, it sends it to the multicast MAC address of the group. Multicast addresses are used for protocols such as ARP (Address Resolution Protocol) and DHCP (Dynamic Host Configuration Protocol).
Broadcast address:
A broadcast MAC address is used to send data to all devices on the network. When a device wants to send data to all devices on the network, it sends it to the broadcast MAC address.
MAC address and IP address:
A MAC address is a hardware address that uniquely identifies a device on a network, while an IP address is a logical address that identifies a device on a network. In other words, a MAC address identifies a device on a network, while an IP address identifies the location of a device on a network.
The relationship between a MAC address and an IP address is that a MAC address is used to identify a device on a local network, while an IP address is used to identify a device on a global network, such as the Internet. When a device sends data to another device on the local network, it uses the MAC address of the destination device. When a device sends data to another device on a global network, it uses the IP address of the destination device.
MAC Address Spoofing:
MAC address spoofing is the act of changing the MAC address of a device to impersonate another device on the network. This is often done for malicious purposes, such as to bypass security measures or to gain unauthorized access to a network. MAC address spoofing is illegal in many jurisdictions.
Conclusion:
In conclusion, MAC addresses are unique identifiers assigned to network interface controllers for use as network addresses in local network communication. They are essential for proper network communication, and can be viewed using a variety of tools. While MAC addresses are assigned by the manufacturer of the device, they can be changed, although doing so is generally not recommended. Understanding MAC addresses is crucial for troubleshooting and network security purposes.