The use of the MAC address is one of the most important aspects of the Ethernet LAN technology. MAC addresses use hexadecimal numbering.
Hexadecimal is a word that is used both as a noun and as an adjective. When used by itself (as a noun) it means the hexadecimal number system. Hexadecimal provides a convenient way to represent binary values. Just as decimal is a base ten number system and binary is a base two number system, hexadecimal is a base sixteen system.
The base sixteen number system uses the numbers 0 to 9 and the letters A to F. Figure 1 shows the equivalent decimal and hexadecimal values for binary 0000 to 1111. It is easier for us to express a value as a single hexadecimal digit than as four binary bits.
Given that 8 bits (a byte) is a common binary grouping, binary 00000000 to 11111111 can be represented in hexadecimal as the range 00 to FF. Leading zeroes are always displayed to complete the 8-bit representation. For example, the binary value 0000 1010 is shown in hexadecimal as 0A.
Note: It is important to distinguish hexadecimal values from decimal values regarding the characters 0 to 9, as shown in Figure 1.
Representing Hexadecimal Values
Hexadecimal is usually represented in text by the value preceded by 0x (for example 0x73) or a subscript 16. Less commonly, it may be followed by an H, for example 73H. However, because subscript text is not recognized in command line or programming environments, the technical representation of hexadecimal is preceded with "0x" (zero X). Therefore, the examples above would be shown as 0x0A and 0x73 respectively.
Hexadecimal is used to represent Ethernet MAC addresses and IP Version 6 addresses.
Hexadecimal Conversions
Number conversions between decimal and hexadecimal values are straightforward, but quickly dividing or multiplying by 16 is not always convenient. If such conversions are required, it is usually easier to convert the decimal or hexadecimal value to binary, and then to convert the binary value to either decimal or hexadecimal as appropriate.
With practice, it is possible to recognize the binary bit patterns that match the decimal and hexadecimal values. Figure 2 shows these patterns for selected 8-bit values.