What's the MAC address?

Source: Internet
Author: User

MAC Address Overview

Mac (media access control), or MAC address, hardware address, used to define the location of the network device. In the OSI model, the third layer of the network layer is responsible for the IP address, and the second layer of the data link layer is responsible for the Mac site. Therefore, a host will have an IP address, and each network location will have a dedicated Mac site. The MAC address, used to represent the identifier of each site on the internet, in hexadecimal notation and a total of six bytes (48 bits). Of these, the first three bytes are the code (high 24 bits) assigned to different manufacturers by the IEEE Registration Authority RA, also known as the "compiled unique identifier" (organizationally unique Identifier), followed by three bytes (Low 24 digits) The adapter interface, which is assigned by each manufacturer to the production, is called an extended identifier (uniqueness). An address block can generate 2^24 a different address. The MAC address is actually the adapter address or adapter identifier EUI-48.

MAC address Explanation

Mac (Medium/mediaaccess control, media access controls) MAC addresses are included in Networkinterfacecard (network card, NIC). The MAC address, also known as the hardware address, is made up of 48-bit/bit (6-byte/byte,1byte=8bits) and 16-digit digits. 0-23 BITS is called the organization Unique identifier (organizationally unique, is the identification LAN (LAN) The identity of the node. The 24-47-bit is assigned by the manufacturer itself. The 48th Digit is the multicast address flag bit. The physical address of the NIC is usually the eprom of the network card manufacturer that burns into the NIC (a flash memory chip, which can usually be erased by the program), which stores the address of the computer and the host that receives the data when transmitting the data.

In other words, the physical transmission of the network at the bottom of the process, is to identify the host through physical address, it must be the world's only. For example, the famous Ethernet card, its physical address is 48bit (bit bit) of integers, such as: 44-45-53-54-00-00, in a machine-readable way into the host interface. Ethernet address management (except in the case of this) (IEEE) (IEEE: Institute of Electrical and Electronic engineers) will be the Ethernet address, that is, 48 bits of different combinations, divided into several separate consecutive address groups, the production of Ethernet network card manufacturers to buy one of the groups, the specific production, Assigns a unique address to an Ethernet card individually.

Figuratively speaking, the MAC address is like the ID card number on our ID card, which has global uniqueness.

The role of MAC address

The IP address is like a job, and the MAC address is like a candidate for the job, position can let a sit, also can let B sit, the same reason a node IP address for the NIC is not to do, basically what kind of manufacturers can use, that is, IP address and MAC address does not exist binding relationship. Some of its own computer mobility is relatively strong, as the same talent can give different units to work the same reason, the mobility of talent is relatively strong. The correspondence between the position and the talent is somewhat like the correspondence between the IP address and the MAC address. For example, if a NIC is broken, it can be replaced without having to obtain a new IP address. If an IP host moves from one network to another, it can give it a new IP address without having to change a new network card. Of course MAC address in addition to only this function is not enough, take human society and network analogy, through analogy, we can find a similar place, better understanding of the role of MAC address. The communication between the computers in the LAN and the WAN is ultimately the result of sending the packet from the initial node of some form of link, from one node to the other, and finally to the destination node. The movement of packets between these nodes is done by ARP (address resolution PROTOCOL: Addressing resolution Protocol) that maps IP addresses to MAC addresses. In fact, human society and the network is similar, imagine in the interpersonal network, a message to Ding, will pass B and C relay, and finally by C to the Ding. In the network, this message is like a packet in a network. Packet in the transmission process will continue to ask the neighboring node MAC address, this process is like the human society message transmission process. I believe that with these two examples, we can further understand the role of MAC address.

Application of MAC Address

Weekday identity cards are not very important, but at some point in time, the identity card is used to prove your identity. For example, you have to go to the bank to withdraw cash, then you need to use the ID card. Then the MAC address and the IP address are bound just as we do in our daily life with our ID card to do important things the same reason. Sometimes, in order to prevent the IP address from being stolen, we can use the simple switch port bindings (static table entries on the Mac table of the port) to prevent the modification of the MAC address theft in the case of a single host on each switch port, if the three-tier device can also provide: switch port/ip/mac The binding of the three to prevent the modification of MAC IP spoofing. General binding MAC address is configured on the switch and router, is the network management personnel can contact, for the general computer users as long as the role of the binding to understand the line. For example, you will not be able to surf the Internet with your laptop in the campus network, this is because the MAC address and IP address (port) binding caused.

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