What is the MAC address? How many bits does a mac address have?

Hello, the MAC address of the office wifi can be viewed on the back of the router, if the wireless IP is used, the MAC address corresponding to each wifi is unique. If you don't know the MAC address, it is recommended that you can set up office WiFi on the mobile phone, [Mobile DingTalk] - [Work] - [Attendance Punch] - [Settings] - [Attendance Group] - [Attendance WiFi] - [Add] You can choose WiFi to add, and the MAC address will be automatically obtained, and multiple office WiFi can be set up without manual input. When adding wifi to your Android phone, the system will automatically recommend all the wifi currently scanned, which is convenient to add quickly (priority recommendation); The iPhone will recommend setting the wifi on the current link of the mobile phone and the wifi linked by the group members.

A MAC address is 48 bits (6 bytes) in length and is usually represented as 12 hexadecimal numbers.

For example, 00-16-ea-ae-3c-40 is a MAC address, where the first 6 hexadecimal numbers 00-16-EA represent the number of the network hardware manufacturer, which is assigned by the IEEE (Institute of Electrical and Electronics Engineers), and the last 6 hexadecimal numbers AE-3C-40 represent the serial number of a network product (such as a network card) manufactured by the manufacturer.

Figuratively speaking, the MAC address is like the ID number on the ID card, which is unique.

The Medium Media Access Control (MAC) address is an identifier used to represent every site on the Internet, in hexadecimal numbers, with a total of six bytes (48 bits). Among them, the first three bytes are assigned by the IEEE's registry RA, which is responsible for assigning ** (high 24 bits) to different vendors, also known as:"A unique identifier on the compilation"(organizationally unique identifier), the last three bytes (the lower 24 bits) are assigned by each manufacturer to the production adapter interface, which is called the extended identifier (uniqueness). An address block can generate 2 different addresses.

The MAC address is actually the adapter address or adapter identifier EUI-48.

The MAC address has 48 bits, which in this case refers to the number of binary bits. However, the representation is expressed in hexadecimal system, and every 4 binary bits become a number in hexadecimal, so it is written (hexadecimal) as 12 bits.

Check it out below:

The devices on the Internet communicate through IP addresses, and in fact, the underlying objects of communication are distinguished by MAC addresses.

Tools: System settings, network card.

1. Generally speaking, the MAC address refers to the MAC of the network card, find the "network" right-click attribute.

2. Enter the network management center, or find the shared network management menu through the control panel.

3. Click to enter the management NIC device and view the local connection properties of the NIC that you need to view.

4. Click on the local connection status to view, the physical address is the MAC address of the computer.

Explain the difference between MAC and IP address

1. For a device on the network, such as a computer or a router, its IP address is variable (but must be unique), while the MAC address is immutable. We can assign any IP address to a host as needed, for example, we can assign an IP address to a computer on a local area network, or we can change it to. Once a network device (such as a network card or router) is produced, its MAC address is always unique and cannot be changed by the user.

2. The length is different. The IP address is 32 bits and the MAC address is 48 bits.

3. The distribution basis is different. The assignment of IP addresses is based on the network topology, and the assignment of MAC addresses is based on the manufacturer.

4. The addressing protocol layer is different. The IP address is applied to the third layer of the OSI, which is the network layer, while the MAC address is used to the second layer of the OSI, which is the data link layer. The link-layer protocol enables data to be passed from one node to another node on the same link (via MAC address), while the network layer protocol enables data to be passed from one network to another (ARP finds the MAC address of the intermediate node based on the destination IP address, transmits it through the intermediate node, and finally reaches the destination network).

Let's put it this way: there is no possibility of running out, MAC address is the address used by the link layer to the network layer, used to identify a host in the same broadcast domain (LAN), a broadcast domain is the range of all interfaces of a switch, out of this range is that the IP address and MAC address have no half-dime relationship, the largest switch I have not seen more than 100 interfaces, but MAC addresses have 2 48, the possibility of conflict is too small. If the network equipment manufacturer can guarantee that the device will not be manufactured with the same MAC address for 10 years, then there is no possibility of conflict at all.

LAN: Several hosts (possibly computers and routers) can be connected to a switch or hub, and when a host wants to send data, a piece of data is formed"MAC address - IP address - destination host port - data"In the form of common Ethernet, the channel you use to send data (such as network cable, wifi) is shared by multiple hosts (there is a little difference when using network cable to connect to the switch, but in essence it is still a shared medium), all hosts will receive the data sent by others (ARP spoofing implementation basis), other hosts will confirm whether the data is sent to themselves through the MAC address, and ordinary terminal hosts (such as mobile phones, computers) will receive this data if they find it their own, otherwise it will be discardedWhen the router receives this data, if there is no path to the destination IP address in its own routing table, it will be discarded, if there is, the MAC address will be stripped and the MAC address of the destination router interface on the next hop network segment will be added, and the next router will be sent to the next router in the same way until it reaches the destination host, so the MAC address will only take effect when the next host is selected, and it will become invalid after reaching the interface of the next host.

Nowadays, we use optical fiber to connect to the Internet network, and the only physical connection between the two hosts is used, and it is no longer a shared media network, but a so-called P2P network, and there is no need for MAC addresses to exist on this network.

To put it simply, it means that the iPhone wants to get the connected device of the LAN (router) where you are located. This feature is designed to protect your local network from scanning devices on your local network indiscriminately by a large number of apps.

In previous versions of iOS, apps could scan devices on their local network at will, so apps could easily get the names and MAC addresses of all devices on their local network. Nowadays, iPhones can already identify specific LANs by Mac addresses.

MAC address is an address that confirms the location of network devices, each network card has a unique MAC address, plus the MAC address is also unique, the device manufacturer will allocate MAC according to a certain rule, so different LANs are unique and can be identified.

IP addresses are logic-based, flexible, hardware-free, and easy to remember. The MAC address is consistent with the hardware to a certain extent, is physical, and can identify a specific network node. Both types of addresses have their own advantages, and they can be used differently depending on the conditions.

Most ways to access the Internet are to organize hosts together through a local area network and then connect to them through devices such as switches or routers and the Internet. As a result, the question arises of how to distinguish between specific users and prevent IP address theft. Since the IP address is only a logical identifier that can be modified by anyone at will, it cannot be used to specifically identify a user.

This is not the case with MAC addresses, which are solidified in the network card. Theoretically, unless the hardware is stolen, i.e., the network card, it generally cannot be impersonated. Based on this characteristic of MAC addresses, the LAN adopts the method of identifying specific users with MAC addresses.