# Hexadecimal Numbers and Broadcast MAC Address
###### tags: `elearning` `Multimedia Wireless Network`
###### Note Page : [:link:](https://hackmd.io/@YTL0307/HJEb6jWCo)

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## **Hexadecimal Numbers**
- IPv4 addresses use decimal numbers, and MAC address and IPv6 use hexadecimal numbers.
- Hexadecimal Format and hexadecimal numbers.
- MAC addresses are expressed in hexadecimal format, a numbering system that uses 16 unique symbols to represent the numbers 0 through 15.
- The hexadecimal numbers 0 through 9 simply represent the numbers 0 through 9 and the hexadecimal letters a through f represent the numbers 10 through 15.
- The hexadecimal numbering system is just another way of representing binary numbers in an easy to read format for humans.
- The tables show each decimal number, the equivalent hexadecimal symbol and its binary equivalent.
- The decimal value of 5 and the hexadecimal value of 5 are the same.
- Each hexadecimal digit or symbol represents 4 bits, which is also known as a nibble (半字節).
- The 4-bit binary equivalent of five, notice that we're doing the same power of 2's math as we did when we converted a binary number into a decimal number.
- This time, however, we're using only 4 bits instead of 8. To represent five in binary, the 4's place and the 1's place are tumed on.
- The decimal number 10, you can see that the hexadecimal symbol 'a' and the decimal value of 10 are not the same.
- In the 4-bit binary equivalent, the 8's place and the 2's place are tumed on and add up to ten.
- To our MAC address and see how to convert each hexadecimal symbol into its binary equivalent.
- The first 3 bytes or first six symbols are easy to convert, because there is a direct mapping from the hexadecimal symbol to the decimal number.
- In the second byte, nine zero, hexadecimal symbol is the same as decimal 9. Therefore, the binary equivalent has the 8's place and the t's place tumed on.
- Hexadecimal symbol 0 is the same as decimal 0, so the second nibble-or group of 4 bits-doesn't have ant bits tumed on.
- Starting with the 4th byte, the hexadecimal symbol 'a' is equivalent to the decimal value of 10.
- Therefore, the binary equivalent of hexadecimal 'a' means that the 8's place and the 2's place must be turned on.
- Hexadecimal symbol f is equivalent to decimal 15. Therefore, the binary equivalent of f means that the 8's place, 4's place, 2 s place and the 1's place must all be tumed on.

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## **Broadcast MAC Address**
- During the Ethernet discussion, we learned that if a device needs to send the same data to every device on the network, it uses a broadcast destination MAC address.
- The broadcast MAC address is where all 48 bits are set to one, or an address consisting of all F's.