What is a MAC address?

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A MAC (Media Access Control) address is a unique identifier assigned to a network interface card (NIC) for use in network communications within a network segment.

Here are the key points to understand about a MAC address:

Definition and Structure
Uniqueness: Each MAC address is intended to be globally unique, ensuring that no two devices on the same network segment have the same address.
Format: A MAC address is typically represented as a series of six pairs of hexadecimal digits, separated by colons (:) or hyphens (-). For example: 00:1A:2B:3C:4D:5E or 00-1A-2B-3C-4D-5E.
Length: It is 48 bits in length, with the first 24 bits representing the Organizationally Unique Identifier (OUI) assigned to the manufacturer, and the last 24 bits representing a unique identifier for the NIC.
Function
Layer 2 Identification: MAC addresses operate at the Data Link layer (Layer 2) of the OSI model. They are used to identify devices on a local network (e.g., Ethernet).
Frame Delivery: They facilitate the delivery of data packets (frames) within the same local area network (LAN). When a device wants to communicate with another device on the same network, it uses the destination device’s MAC address to ensure the data is sent to the correct place.
Use Cases
Ethernet and Wi-Fi:
MAC addresses are used in various types of network technologies, including Ethernet and Wi-Fi.
Switch Operations: Network switches use MAC addresses to forward data frames to the correct destination within the LAN. They maintain a MAC address table to map each MAC address to the corresponding port on the switch.
Examples and Representation
Hexadecimal Digits: Since MAC addresses are expressed in hexadecimal, each pair of digits can range from 00 to FF. An example MAC address could look like 00:1A:2B:3C:4D:5E.
Broadcast and Multicast: Certain MAC addresses are reserved for specific purposes. For example, FF:FF:FF:FF:FF:FF is the broadcast MAC address used to send frames to all devices on the network. Similarly, there are reserved addresses for multicast.
Practical Considerations
Static and Dynamic Assignment: MAC addresses are usually assigned by the manufacturer and are static. However, some systems allow for MAC address changes or „spoofing” for various purposes.
Security Implications: MAC addresses can be used in network security measures such as MAC address filtering to control access to a network. However, they can be spoofed, which is something to consider in security planning.
A MAC address is a critical component of network hardware, ensuring devices can be uniquely identified and communicated with on a local network.

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