Introduction of MAC Address in Computer Network
We require an address in order to communicate with or transfer data between computers. Different types of addresses are introduced in computer networks; each operates at a different layer. A physical address that operates at the Data Link Layer is called a Media Access Control Address. We will talk about addressing DLL, or MAC Address, in this article.
A physical address called a Media Access Control (MAC) address operates at the OSI model’s data link layer.
- A MAC address is a 48 or 64-bit address associated with a network adapter.
- Because MAC addresses are associated with the physical components of network adapters, they are also referred to as “hardware addresses” or “physical addresses.”
- MAC addresses uniquely identify the adapter on the LAN.
- Hexadecimal representation are used to represent MAC addresses. A 48-bit address might be “01-23-45-67-89-AB” or a 64-bit address might be “01-23-45-67-89-AB-CD-EF.” Occasionally, colons (:) are utilised in place of dashes (-).
- Although MAC addresses are frequently thought of as permanent, they can occasionally be changed.
There are three types of MAC addresses −
- Unicast MAC Address
- Multicast MAC address
- Broadcast MAC address
Format of MAC Address
The MAC Address is a 12-digit (6-byte) hexadecimal number that is typically written using colon-hexadecimal notation. The MAC Address’s first six digits, such as 00:40:96, identify the manufacturer, known as OUI (Organizational Unique Identifier). These MAC prefixes are given to the registered vendors by the IEEE Registration Authority Committee.
Here are some OUI of well-known manufacturers :
CC:46:D6 - Cisco
3C:5A:B4 - Google, Inc.
3C:D9:2B - Hewlett Packard
00:9A:CD - HUAWEI TECHNOLOGIES CO.,LTD
Network Interface Controller is identified by the manufacturer’s six rightmost digits.
Colon-Hexadecimal notation is used to represent the MAC address, as was previously mentioned. But it’s not necessary; this is just a conversion. Any of the following formats can be used to represent a MAC address:
Note: Linux OS uses colon-separated hexadecimal notation, while Cisco Systems uses period-separated hexadecimal notation.
How to find MAC address
Command for UNIX/Linux -ifconfig -aip link list ip address show
Command forWindows OS - ipconfig /all
MacOS - TCP/IP Control Panel
Types of MAC Address:
1. Unicast: Any interface leading to a particular NIC is the only one to which a Unicast addressed frame is sent. When the LSB (least significant bit) of an address’s first octet is set to zero, only one receiving NIC is intended to receive the frame. The source machine’s MAC address is always Unicast.
2. Multicast: The source can send a frame to a number of devices by using the multicast address. The LSB (least significant bit) of the first octet of an address is set to one in Layer-2 (Ethernet) Multicast addresses. For use by standard protocols, IEEE has designated the address block 01-80-C2-xx-xx-xx (01-80-C2-00-00-00 to 01-80-C2-FF-FF-FF) for group addresses.
3. Broadcast: Broadcasting is also possible on the underlying layer, similar to Network Layer ( Data Link Layer). Broadcast addresses are Ethernet frames with all bits of the destination address set to one (FF-FF-FF-FF-FF-FF). Every computer connected to that LAN segment will receive frames with the destination MAC address FF-FF-FF-FF-FF-FF.
What is MAC Cloning
Some ISPs use MAC addresses to give the gateway device an IP address. The DHCP server logs the MAC address of the connected device and then assigns an IP address. The MAC address will now be used to identify the system. The device loses its IP address when it is disconnected. The DHCP server determines whether the device has previously been connected when a user requests a reconnect. The server then tries to assign the same IP address if that is the case (in case the lease period has not expired). If a user changes their router, they must inform the SP of the new MAC address because the ISP is unaware of the new MAC address and thus cannot establish a connection.
The user may also choose to clone the ISP-registered MAC address as an alternative. There is no connection issue because the router continues to send the outdated MAC addresses to the ISP.
Characteristics of MAC address
The Media Access Control protocol sub-layer uses the Media Access Control address (MAC address), a distinctive identifier most network adapters or network interface cards (NICs) are given by the manufacturer. A 48-bit binary value represented by 12 hexadecimal digits is an Ethernet MAC address (4 bits per hexadecimal digit). Since MAC addresses have a flat structure, they cannot be routed on the Internet. MAC addresses are not used on serial interfaces. A network and host portion with the address is NOT present. It is employed to deliver the frame to the target gadget.