What is a MAC address?

A MAC address (Media Access Control Address) is a unique identifier assigned to a network interface card (NIC). It is usually represented by six groups of two-digit hexadecimal numbers. MAC addresses are used in local area networks (LANs) to identify devices and ensure that data can be accurately transmitted to the target device.

Features of MAC addresses:

Hardware level: 

MAC address is an address used to identify network devices at the hardware level (data link layer).

Fixed: Generally, MAC addresses are permanent, and hardware manufacturers assign a unique MAC address to each network interface card at the time of production.

LAN communication: 

MAC addresses are mainly used for internal communication within a LAN. When data packets are transmitted in a LAN, devices use MAC addresses for identification and forwarding.

What is an IP address?

An IP address (Internet Protocol address) is a logical address assigned to a network device to enable Internet communication. It is used to locate and identify devices on the network. There are two main versions of IP addresses: IPv4 and IPv6. IPv4 addresses are represented by four decimal numbers, while IPv6 addresses are represented by eight groups of hexadecimal numbers.

Characteristics of IP addresses:

Network level: IP addresses are addresses used to identify devices at the network layer (layer 3).

Dynamic: 

IP addresses can be static (permanently assigned) or dynamic (automatically assigned via DHCP). This means that a device may get a different IP address each time it connects to a network.

WAN communication: 

IP addresses are used for Internet and WAN communication to ensure that data packets can find the target device when traveling between different networks.

How do MAC addresses and IP addresses work?

When computers, tablets, and smartphones connect to a home Wi-Fi network, they each get an internal IP address from the router. Within the local area network, this IP address is unique to each device and is used by the router to distinguish the starting and ending points of data transmission on the network.

When these devices communicate with the Internet, the router uses network address translation (NAT) technology to allow multiple devices to share a public IP address assigned by the Internet service provider. When a device makes an external request, the router translates the private IP address into a public IP address and records the translation using a NAT table that associates the private IP address and a specific port number with the public IP address. This association is critical because it allows the router to track the status of each connection.

When data is returned from the Internet to the public IP address, the router queries the NAT table to determine which device on the LAN the data should be sent to. It checks the port number in the packet header information that was previously associated with the device's outgoing request. Based on this information, the router translates the public IP address back to the corresponding private IP address, thereby correctly transmitting the received data to the target device. This process allows each device to communicate as if it were directly connected to the Internet, while all devices share a public IP address.

Difference between MAC Address and IP Address

Operational Level: 

MAC addresses work at the data link layer to enable communication within the LAN; while IP addresses work at the network layer, allowing devices to connect across different networks on the Internet.

Format: 

MAC address is a 48-bit hexadecimal number, usually divided into six groups separated by colons; in contrast, IP address has two forms, IPv4 address is a 32-bit number, divided into four groups of decimal display, and IPv6 address is a 128-bit hexadecimal number, divided into eight groups.

Allocation method: 

MAC address is the address permanently assigned to the network interface card when the device leaves the factory, which is a physical address; IP address can be statically assigned by the administrator or dynamically assigned by the DHCP server.

Use: 

MAC address is essential for the local transmission of data packets within the network; IP address is used to identify devices and ensure that data packets are correctly routed throughout the Internet.

Application scope: 

MAC address is only valid and used within the local area network and will not cross routers; while IP address is used for global communication and can cross multiple networks.

Visibility and propagation: 

During the transmission of data packets, MAC address is mainly used and visible in its original network, and will change when passing through routers; but IP address remains unchanged from the starting point to the end point.

Changeability: 

Although MAC addresses are usually fixedly associated with device hardware, they can be forged; in contrast, IP addresses are more flexible and can be easily changed or reassigned.

Conflict resolution: 

Since MAC addresses are uniquely assigned by manufacturers, MAC address conflicts are extremely rare; IP address conflicts are relatively common, but can be resolved by network reconfiguration or using DHCP.

MAC addresses and IP addresses each play different roles in the network. Although they are both used to identify devices, they have significant differences in function, structure, and usage scenarios. Understanding these differences not only helps with network management and maintenance, but also provides important basic knowledge for our operations in the digital world. By deeply understanding these two identities, we can better ensure network security, optimize network performance, and improve our network experience.