The relationship between Mac and IP

Source: Internet
Author: User
What is a MAC address? Today on the Internet to find information, organized a bit, to share with you:
As for MAC address, because we do not contact with it directly, so we are not necessarily very familiar with. Many computers are now connected by building a local area network first and then through a switch and the Internet. Each user is then assigned a fixed IP address, unified management by the central administration, so as to facilitate the management of the need to use the MAC address to mark users, prevent confusion, clear responsibility (such as cybercrime). In addition, the IP address and MAC address are different, although they are one by one corresponding relationship in the LAN. IP address is according to the current IPV4 standard, not limited by hardware more easily memory address, and MAC address is using the physical address of the network card, how much with the hardware, more difficult to remember. The MAC (media access control, media access controls) address is the identity of the LAN (LAN) node identification. The MAC address is the physical address of the serial eeprom that is cured on the network card, usually 48 bits long. (separated by a colon for every 2 16 numbers, such as: 08:00:20:0A:8C:6D is a MAC address where the top 6 16 binary digits 08:00:20 represents the network hardware manufacturer's number,
It is allocated by the IEEE (Istitute of Electrical and Electronics Engineers, Institute of Electrical and Electronics Engineers), and the 3-bit 16-digit number 0A:8C:6D represents the serial number of a network product (such as a network adapter) manufactured by the manufacturer. Each network manufacturer must ensure that each Ethernet device it manufactures has the same first three bytes and a different last three bytes. This ensures that every Ethernet device in the world has a unique MAC address.
Since each Ethernet device has a unique MAC address at the factory, why do I need to assign an IP address to each host again? Or why each host is assigned a unique IP address, why also in the network equipment (such as NIC, Hub, router, etc.) when the production of a unique MAC address.
There are several main reasons for this:
(1) The allocation of IP addresses is based on the topology of the network, and not on who created the network settings.
It is not feasible to build an efficient routing scheme on the basis of the device manufacturer rather than the topology location where the network is located.
(2) When there is an additional layer of address addressing, the device is easier to move and repair. For example, if an Ethernet card 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.
(3) The communication between the computers in the LAN and the WAN is the result of sending the packet from the initial node of some form of link, transferring from one node to another node, and finally transmitting 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. The Ethernet switch implements packet Exchange and delivery based on the MAC source address and Mac destination address in the header of a message. 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, at the bottom of the network physical transmission process, is through the physical address to identify the host, it is generally the only global. 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 (IEEE) 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, the unique address given to the Ethernet card. Figuratively speaking, the MAC address is like the ID card number on our ID card, which has global uniqueness. To build a local area network, we must learn to bind IP and MAC address, change the new network card, must learn to modify the MAC address to deal with the embarrassment of not surfing the Internet. Don't let the MAC address become a stumbling block to your online life. I believe that through my introduction, everyone will have a full understanding of the MAC address.
Get Mac for this machine
For a few machines, we can get MAC addresses like this: In Windows 98/me, click start → run → enter "winipcfg" → carriage return.
In Windows 2000/XP, click "Start" → "Run" → enter "CMD" → return → enter "Ipconfig/all" → carriage return.
How do I bundle MAC addresses and IP addresses?
MAC address is the unique identity of the network card, this uniqueness is to bring the Gospel of Internet management, because by bundling IP and MAC address, it can easily prevent the network IP address embezzlement phenomenon, prevent illegal intruders.
For dynamic IP, do a DHCP server to bind the user network card MAC address and IP address, and then set permissions according to different IP; for static IP, if you use the three-tier switch, you can do the IP address on each port of the switch, so if you change the IP address of a client, The PC will not be able to connect to the network.
Static IP address binding as an example, to achieve the above tricks: assume that at this time the NIC MAC address for 44-45-53-54-00-00. Suppose we are in the Windows 98 operating system, after starting virtual DOS, type "ARP space-s space space 44-45-53-54-00-00", enter. This realizes the static IP address and the network card address is the 44-45-53-54-00-00 computer bundle, next we look at the ARP commonly used parameter table.
Special Note: ARP command only in the LAN Internet Proxy server side useful, but also if static IP address. If you are a network administrator, you have to the MAC address and IP binding, so as to eliminate a lot of hidden dangers.
Big overhaul of Mac
MAC address is sacred and inviolable. However, for the replacement of the new network card friends, it really can not use the original IP it. There is still a way.
Take the common Windows 2000/xp for example:
The first step, click "Start" → "Run" → enter "Regedit", open Registry Editor, press Ctrl+f to open the Find window, enter "DriverDesc" click OK. Double-click what you find, that is, a description of the information you want to modify, and a list of the left to display the current primary key (for example, 0000).

The second step, under the corresponding 0000 new string of values, named NetworkAddress, the key value set to the MAC address you want, note to write continuously, such as 112233445566.

The third step, restart the computer, you will find that the NIC MAC address has changed to the address you set. However, if you want to change the address frequently, the method of changing the registration list is too cumbersome. Don't worry, the following two changes will make you realize that it's so easy to change your MAC address later.

In the fourth step, add an item in the corresponding 0000 ndi\\params, the primary key is named NetworkAddress, and then under the primary key is added a string value named Default, which is set to the MAC address you want to set, as well as continuous write. Fifth step, under the NetworkAddress primary key, continue to add a string named Paramdesc, whose value can be set to "MAC address".
All settings complete, close the registry, restart the computer, open the "Network Neighborhood" properties, select the appropriate network card, click "Properties" to select the "Advanced" tab, the property will be more than the MAC address option, that is, in the second step in the registry added to the NetworkAddress , it is OK to modify the MAC address in the setting value here only. The Windows 9x modification method is very similar and we will not discuss it here. Finally the MAC address to complete the whole thing to introduce to everyone. It is worth reminding you that the original address must be recorded before modifying the local MAC address, or back up the registry, otherwise the original address can only be reinstalled. And for their own changes in the MAC address network, network administrators still have the means to detect. Therefore, do not forget to change the network card to say hello yo.
Read some more information, you can also:
Go to the command prompt and enter the command at the command prompt: Arp-s 00-10-5c-ad-72-e3, the MAC address and IP address can be bundled together.
In this way, the IP address will not be stolen and can not use the normal campus network situation (of course, there will be no error message dialog box), can effectively guarantee the campus network security and user application.
Note: The ARP command is only useful for the Internet Proxy Server on the LAN, and it is for static IP address, if modem dial-up or dynamic IP addresses do not work. The functions of each parameter of the ARP command are as follows:


-S: Binds the corresponding IP address to the physical address, as the example in this article.

-D: Deletes the corresponding IP address and the physical address bundle.

-A: Displays the IP address and the corresponding physical address situation by querying the ARP protocol table.
3.IP address and physical address in pairs is stolen what's going on?

For example, in the LAN, by the host automatically assigned IP address, or their own designated IP address, automatic allocation, first open the host, and then the next open the machine automatically assigned IP for ... To push down, or their own designated IP, such as, Host (1th) for the,2 number machine for 168.192 0.2, in order to push down, in the local area network, IP address allocation in the case, for example, I now do is the 5th machine, Originally IP should be, but when I set the specified IP, I change to, so that is equivalent to say, occupy the IP of the 2nd machine, when the 2nd machine restart, it will appear that the IP is occupied, unable to connect to the network, resulting in network or network share access, In simple terms, this is the solution, that is, the IP and the local network card MAC address bundle, so that other occupy not.

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.