What is MAC Address? Why do we need this

MAC stands for Media Access Control. The MAC address, also known as the physical or hardware address, is a unique value associated with a network adapter called a NIC. The MAC address is engraved on NIC at the time of manufacturing and thus it is a permanent address and cannot be changed under any circumstances. The machine on which the NIC is attached can be physically identified on the network using its MAC address.

  • MAC address is the physical address, which uniquely identifies each device on a given network. To make communication between two networked devices, we need two addresses: IP address and MAC address. It is assigned to the NIC (Network Interface card) of each device that can be connected to the internet.
  • Media Access Control and is also known as Physical address, hardware address, or BIA (Burned In Address).
  • It is globally unique; it means two devices cannot have the same MAC address. MAC Add is represented in a hexadecimal format on each device, such as FC:F8:AE: CE:7B:16.
  • MAC is 12-digit, and 48 bits long, out of which the first 24 bits are used for OUI(Organization Unique Identifier), and 24 bits are for NIC/vendor-specific.
  • It works on the data link layer of the OSI model.
  • It is provided by the device’s vendor at the time of manufacturing and embedded in its NIC, which is ideally cannot be changed.
  • The ARP protocol is used to associate a logical address with a physical or MAC address.

Each MAC address is a 12-digit hexadecimal number (48 bits in length), of which the first six digits (24 bits) contain the manufacturer’s ID called Organisational Unique Identifier (OUI) and the later six digits (24 bits) represent the serial number assigned to the card by the manufacturer. A sample MAC address looks like this:

Why do we need this?

As we already had the IP address to communicate a computer to the internet, why do we need the MAC address? The answer to this question is that every mac address is assigned to the NIC of a hardware device that helps to identify a device over a network.

When we request a page to load on the internet, the request is responded to and sent to our IP address.

Both MAC and IP addresses are operated on different layers of the internet protocol suite. The MAC address works on layer 2 and helps identify the devices within the same broadcast network (such as the router). On the other hand, the IP addresses are used on layer 3 and help identify the devices on different networks.

We have the IP address to identify the device through different networks, we still need a MAC address to find the devices on the same network.

Types of MAC address

There are three types of MAC addresses, which are:

  1. Unicast MAC Address
  2. Multicast MAC address
  3. Broadcast MAC address

1. Unicast MAC address:

The Unicast MAC address represents the specific NIC on the network. A Unicast MAC address frame is only sent out to the interface which is assigned to a specific NIC and hence transmitted to the single destination device. If the LSB (least significant bit) of the first octet of an address is set to zero, the frame is meant to reach only one destination NIC.

2. Multicast MAC Address:

Multicast addresses enable the source device to transmit a data frame to multiple devices or NICs. In Layer-2 (Ethernet) Multicast address, LSB (least significant bit) or first 3 bytes of the first octet of an address is set to one and reserved for the multicast addresses. The rest 24 bits are used by the device that wants to send the data in a group. The multicast address always starts with the prefix 01-00-5E.

3. Broadcast MAC address

It represents all devices within a Network. In broadcast MAC address, Ethernet frames with ones in all bits of the destination address (FF-FF-FF-FF-FF-FF) are known as a broadcast address. All these bits are the reserved addresses for the broadcast. Frames that are destined with MAC address FF-FF-FF-FF-FF-FF will reach every computer belonging to that LAN segment. Hence if a source device wants to send the data to all the devices within a network, that can use the broadcast address as the destination MAC address.

How to find the MAC address of a device

Windows:

  1. Click Start > Control Panel > Network and Internet > Network and Sharing Center.
  2. Then Click the network you would like to view the MAC address for.
  3. Click Details.
  4. The MAC address is listed under the Physical Address heading.

Linux:

  1. Open a terminal or console window.
  2. Type ifconfig.
  3. The MAC address is listed as HWaddr in the format of 12:34:56:78:AB.

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