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What is MAC address or Layer 2 addresses or physical address

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Media Access Control (MAC address or Layer 2 addresses or physical address or hardware address) addresses are 48 bit (six bytes) binary addresses represented in hexadecimals. The purpose of representing the binary address in hexadecimal format is to make it easier for humans to read and understand. MAC addresses are theoretically permanent numbers, which are burned into the network card.

MAC addresses are typically locally specific, means that the scope of a MAC address is limited within a Local Area Network (LAN).

For example, the MAC address 10101010.11110000.11000001.11100010.01110111.01010001 in binary can be represented as shorter hexadecimal equivalent AA.F0.C1.E2.77.51.

In a MAC address, one hexadecimal digit resembles a group of four contiguous binary bits, called a nibble. The first nibble 1010 from the left most byte in above example represent the first equivalent hexadecimal A in its hexadecimal representation, and the second nibble 1010 from the left most byte in above example represent the second equivalent hexadecimal A in its hexadecimal representation.

The first three bytes of the MAC address identifies the vendor who manufactured the product (Example: a NIC Card), and is known as OUI (Organizationally Unique Identifier). You can search for the OUI listings in following URLs.

http://standards.ieee.org/develop/regauth/oui/public.html

or

http://www.coffer.com/mac_find/

Refer the following table for easy conversion from binary to decimal and hexadecimal numbers.

Decimal Binary Hexadecimal
0 0 0
1 1 1
2 10 2
3 11 3
4 100 4
5 101 5
6 110 6
7 111 7
8 1000 8
9 1001 9
10 1010 A
11 1011 B
12 1100 C
13 1101 D
14 1110 E
15 1111 F

• MAC Address FF:FF:FF:FF:FF:FF is reserved for Broadcast type of communication. An Ethernet Switch will flood an Ethernet Frame with FF:FF:FF:FF:FF:FF as the destination MAC Address to all its connected ports.

• MAC Addresses 01:00:5E:00:00:00 - 01:00:5E:7F:FF:FF are reserved for IPv4 Multicast.

• MAC Addresses of the range 33:33:xx:xx:xx:xx are reserved for IPv6 Multicast.

              Jajish Thomason Google+
Related Topics
TCP/IP Network Access Layer Media Access Control (MAC) addresses TCP/IP Internet Layer IP Addresses
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