MAC address Summary

 

The MAC address in the IPv4 environment has become a common topic. Here is a summary and sharing.

 

In the TCP/IP architecture, MAC addresses play a very important role. In communication, the host Nic identified by the MAC address serves as the hardware address of the host identity. After each network card is produced, it will be identified by a globally unique ID and will not be repeated. This number is the MAC address, that is, the physical address of the network card. The MAC address consists of 48-bit binary numbers, that is, 6 bytes. It is represented in hexadecimal notation in communication. The first 24 digits are the manufacturer code applied by the manufacturer to the IEEE Standard Organization. They are fixed, but the eighth digit must be 0 because of the physical address of the NIC, it must be a unicast address. In an IPv4 environment, the unicast and multicast addresses are binary digits of the eighth digit of the verification. 0 represents the unicast address, and 1 represents the multicast address. In hexadecimal notation, the second digit in the first byte must be an even number (decimal ). That is to say, the second number must be one of 0, 2, 4, 6, 8, A, C, and E, so it is much easier to distinguish unicast or multicast addresses.

 

Example: 6C-62-6D-26-1E-29: its binary:

 

01101100-01100010-01101101-00100110-00011110-00101001 unicast: the eighth digit is 0.

 

We know that the IPv6 IP address is a 64-bit binary number. At the beginning of IPv6 development, it mainly aims to solve the problem of IPv4 address insufficiency, we are pleasantly surprised to find that IPv6 functions are more than just these. The ing between IPv6 and MAC addresses is a bright spot, it also solves the problem of redundant MAC address and IP address ing mechanisms and provides a simple algorithm for automatic IP Address allocation, this makes it simple and does not cause any conflict (because the MAC address is unique ).

 

Let me introduce how they build mappings.

 

We know that the MAC address is a 48-bit binary number, while the IPv6 IP address is 64-bit, with a difference of 16 digits in the middle. This will cause a lot of trouble for ing, so after discussion by scientists and manufacturers, the NIC address will be upgraded to 64-bit in the future, in this way, a unique ing can be easily established through a certain mathematical algorithm, which greatly improves the convenience of communication. However, the current 48-bit ing method has been released:

 

It inserts a fixed 16-bit value between two 24-bit NICs: 11111111-11111110 to realize compatibility with old NICs.

 

References: video tutorial WANG Xi-IPv6 overview and getting started.

 

Address: http://www.microsoft.com/china/technet

 

Welcome to comments.

 

 

 

 

 

This article is from the "Yu zichen-IT Road" blog