Why use MAC address when we have IP address?

IP address and MAC address are both very important concepts in network communications.

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IP address refers to Internet Protocol address, which is a unified address format provided by IP protocol. A logical address is assigned to each network and each host on the Internet to mask the difference in physical addresses. IP addresses can be used for user login, network addressing, data transmission, security protection, routing and other aspects. For example, when a user enters an IP address in the network, the server can verify the user's identity and allow him to access specific resources; IP addresses can also be used to find devices in the network so that they can be connected to the network; IP addresses are also used to indicate which port number a data packet is sent from and how the data packet should be routed; IP addresses can also be used to ensure the security of the network and prevent unauthorized devices from accessing the network. IP addresses can be changed, and the allocation of addresses is based on the network topology.

The MAC address is the physical address of a network device, which is written inside the hardware by the network device manufacturer when it is produced. It is used to uniquely identify a network card in the network. If a device has one or more network cards, each network card needs and will have a unique MAC address. MAC addresses are usually used for access control, security, and routing. For example, MAC addresses can be used to limit device access, associating MAC addresses with user accounts to ensure that only authorized users can access network resources; MAC addresses can also be used to authenticate devices to ensure that only authorized devices can access network resources; when a device passes through a router, the router will match the IP address with the MAC address to ensure that the data packet is correctly forwarded to the target device. The MAC address is unique, and the MAC address of each hardware is fixed when it leaves the factory, so many application software are developed around the MAC address.

IP addresses and MAC addresses each carry unique missions in computer networks. Their functions and uses complement each other and together ensure smooth network communications.

"IP address, as a logical address of the network layer, plays a core role in identifying and locating network devices." It allows devices to communicate with each other in the vast Internet space and realize the transmission and sharing of information. The hierarchical structure of IP addresses, including the network part and the host part, enables data packets to be routed and addressed in a complex network environment, ensuring that data can accurately reach the target device. In addition, as a logical address, IP address is flexible and changeable, and can be changed and reallocated as needed, which facilitates the movement of devices and network changes.

"MAC address, as the physical address of the network interface device, is unique and fixed." It plays a vital role in the data link layer and is used to uniquely identify and locate devices in the local area network. The MAC address is the inherent identity of the device, which is assigned by the manufacturer when the device is produced and has the characteristic of being difficult to change. This makes the MAC address a permanent identity of the device in the network, providing a stable and reliable foundation for network communication.

In network communications, IP addresses and MAC addresses each have their own importance and uses:

1. When devices communicate in a network, they use IP addresses to locate each other and pass data packets.
2. MAC addresses are used for direct communication within a local area network, for example, in Ethernet, the destination MAC address of a packet is used to deliver the packet directly to the destination device.
3. Network devices (such as switches) use MAC addresses to forward data within a local area network, while routers use IP addresses to forward data between different networks.

IP addresses and MAC addresses each play an important role in computer networks. IP addresses are used to identify and locate network devices to achieve cross-network communication; while MAC addresses are used to uniquely identify and locate devices within a local area network to ensure direct data transmission. The combined use of the two provides a stable, efficient and accurate guarantee for network communication. Both the logical addressing of IP addresses and the physical identification of MAC addresses are indispensable and important components of computer networks.