MAC (Media Access Control) Address is used to uniquely identify NICs(Network Interface Cards) in a network. The MAC is heavily used by the Layer 2 Ethernet protocol and assumed as defacto protocol for Layer2 communication. The MAC address consists of 48 bits hexadecimal value. Every mac address is unique in the world theoretically but the reality can be a bit different. Some manufacturers may use a single MAC address multiple times for different NICs or Ethernet cards.
MAC Address Structure
MAC address consists of 48 bits but it is expressed in a more human friendly. As you accept printing the MAC address like “101001010101010…10101” with 48 characters is not a practical way. The hexadecimal values are used to express the MAC address in a more readable and practical format. As an example 01:00:5f:ab:cc:de is a MAC address that uses the double colons in order to separate grouped hexadecimal values. The MAC address can be grouped with 2 hexadecimal values and a separate is used between them.
MAC addresses are created by using two-part where the first part is the Organizationally Unique Identifier or OUI in order to describe the assigned manufacturer which can use the provided MAC address range without a problem. The OUI provides the ability to divide the whole MAC address space in easier to manage parts and provides the management to the assigned manufacturers.
Organizationally Unique Identifier
The Organizational Unique Identifier consists of 24 bits of the MAC address. In other words, it consists of 6 hexadecimal values. The remaining part of the MAC address is managed by the assigned manufacturer. In the following example
11:22:33 is the OUI of the mac address and
AA:BB:CC is the random address part.
The OUI is managed by the
IEEE and there is a database that can be also accessed via inter in order to check the OUI part of the MAC addresses. The following link can be used to check the OUI of a MAC address.
Also popular network capture tool Wireshark provides the ability to search multiple MAC addresses OUI and manufacturers via the following web page.
OUI For Well Known Manufacturers
Below you can see well-known manufacturers’ OUI’s. Following is just an example and a single manufacturer may own multiple OUI according to its manufacturing numbers.
00:00:01 Xerox Xerox Corporation 00:01:42 Cisco Cisco Systems, Inc 00:09:0F Fortinet Fortinet Inc. 04:BA:8D SamsungE Samsung Electronics Co.,Ltd
MAC Address Formats
MAC Addresses can be presented in different formats. But the most popular format is using double colons or dashes for each group of hexadecimal which consists of two hexadecimal.
11:22:33:AA:BB:CC 11-22-33-AA-BB-CC 11.22.33.AA.BB.CC 1122.33AA.BBCC 112233AABBCC
Ping MAC Address
The MAC address can be pinged by using tools like
arping . In the following example, we ping a MAC address using arping command.
$ sudo arping 00:50:56:EE:E2:9D