IP and Mac

MAC address:

In the OSI (Open System Interconnection) layer-7 Network Protocol Reference Model (1), the second layer is the data link ). A mac address is also called a physical address, hardware address, or link address. It is written into the hardware when produced by a network device manufacturer. Both the IP address and MAC address are in binary format on the computer. The IP address is 32 bits, while the MAC address is 48 bits. The MAC address is 48 characters long (6 bytes). It is usually expressed as 12 hexadecimal numbers. Each two hexadecimal numbers are separated by colons, for example: 08: 00: 20: 0a: 8c: 6d is a MAC address. The first six digits of the hexadecimal number 08:00:20 represent the number of the network hardware manufacturer.
Engineers Association), and the last six hexadecimal 0a: 8c: 6d represents the serial number of a network product (such as a NIC) manufactured by the manufacturer. As long as you do not change your MAC address, your MAC address is the only one in the world.

Communication between computers in the LAN or Wide Area Network eventually means that data packets are transmitted from one node to another from the initial node on a certain form of link, finally transmitted to the target node. ARP (Address Resolution Protocol: Address Resolution Protocol) is responsible for ing IP addresses to MAC addresses.

Mac scanners can obtain the physical addresses of computer NICs in batches;

Change the MAC address:

You can modify your MAC address in either hardware or software. The hardware method is to directly operate the NIC, modify the MAC address saved in the EPROM of the NIC, and change the address in the memory through the modification program provided by the NIC manufacturer. So what is EPROM? EPROM is a storage term used in electronics. It is erasable. That is to say, you can use a pen to write a piece of white paper, and then you cannot use an eraser, the EPROM can be erased after being written in a pencil, and the data storage can be changed repeatedly. Of course, the software modification method is much simpler. In Windows, the MAC of the NIC is stored in the registration
The table is actually extracted from the Registry, so you only need to modify the Registry to change the Mac.

Modify in Windows 2000/XP: Open the Registry Editor, HKEY_LOCAL_MACHINE/system/CurrentControlSet/control/class/4d36e970-e325-11ce-bfc1-08002be10318, 0002, driverdesc, if found in 0000, add a string variable under 0000 and name it "networkaddress". The value is the MAC address to be set, for example: 000102030405

After completing the preceding operations, restart the instance. Generally, the source MAC address of the packet sent by the network adapter is not written by the network adapter, but provided by the application. In general implementation, the application obtains the MAC address from the network adapter first, this Mac is used as the source MAC for each sending, And the MAC address in the registry is read from the NIC during Windows installation. As long as your operating system is not reinstalled, it should not be a problem.

Sometimes, in order to prevent IP addresses from being stolen, we can bind them through a simple switch port (the Mac table of the port uses static table items ), you can prevent MAC address tampering when each vswitch port is connected to only one host. For a layer-3 device, you can also bind the port, IP address, and Mac of the vswitch, prevents mac ip address theft. For example, if you change your laptop to another dormitory on the campus network, you cannot access the Internet. This is caused by the binding of the MAC address and IP address (port.