In a TCP/IP network, a computer needs to obtain an IP address in order to function properly, and this process is called IP address assignment. There are three common IP address assignment modes: static assignment, dynamic assignment, and zero configuration.
Static IP assignment:
Static allocation is also known as manual allocation. In this way, the network administrator sets the IP address to be used directly in the computer. In Windows, you can manually configure a static address in the Internet Protocol Version 4 (TCP/IPv4) Properties dialog box. By checking the "Use the following IP address (S)" check box, users can enter the desired IP address, subnet mask, and default gateway. This information must match the configuration of the network on which it resides. In this mode, the IP address is not automatically changed and remains unchanged.
1. Dynamic IP address assignment
Dynamic IP address assignment is a flexible IP address assignment method in which computers obtain an IP address by sending a request to the DHCP server and use the address for communication after successfully obtaining it. In this process, the computer is treated as a DHCP client, and the DHCP server is responsible for managing and assigning IP addresses.
Specifically, the dynamic IP assignment process is as follows:
After a computer starts up or joins the network, it sends a DHCP request broadcast, called a DHCP Discover message, to find available DHCP servers.
After receiving a DHCP Discover message, the DHCP server replies with a DHCP Offer message that contains an available IP address and other configuration information, such as a subnet mask, gateway address, and DNS server address.
After receiving the DHCP Offer message, the computer selects an IP address and sends a DHCP Request message to the DHCP server to request the assignment of the IP address.
After receiving a DHCP Request message, the DHCP server confirms that the IP address has not been assigned to another device and sends a DHCP Ack message to the computer to indicate that the IP address is successfully assigned to the computer.
After receiving the DHCP Ack message, the computer uses the assigned IP address to communicate.
The characteristic of dynamic IP assignment is that the IP address obtained by the computer is not permanent, but valid for a certain lease period. Once the lease expires, the computer releases the IP address and returns it to the DHCP server. If the computer still needs to work, it will re-request a new IP address from the DHCP server, which may cause the computer's IP address to change.
In Windows, users can easily configure dynamic IP assignment. Just select the "Automatically obtain an IP Address (0)" and "Automatically Obtain a DNS Server address (B)" check boxes in the "Internet Protocol Version 4 (TCP/IPv4) Properties" dialog box, and the computer will automatically request and obtain an IP address from the DHCP server without manual setting.
The advantage of dynamic IP allocation is its flexibility and efficiency. It is suitable for large-scale networks, especially in cases where devices need to be added or removed frequently, dynamic IP allocation can automatically manage IP addresses, avoiding the tedious and potential errors of manual configuration. However, because IP addresses can change, this also makes some specific applications or services need additional processing to adapt to dynamic IP changes. In summary, dynamic IP allocation is widely used in modern networks, which brings convenience and efficiency to network management.
2, zero configuration:
In dynamic assignment mode, if the DHCP server is offline or faulty, the client cannot obtain the IP address. In order to solve this situation, some systems use the zero-configuration technique to assign themselves a private address in the range of 169.254.0.0 to 169.254.255.255. This Private address is an automatically configured address in the local network, called Automatic Private IP Addressing (APIPA), that allows computers to continue communicating in certain situations, even if there is no formal IP address assignment. Zero-configuration technology allows computers to communicate even when they cannot obtain a valid IP address.
Static IP address assignment mode requires manually setting IP addresses and the IP addresses remain unchanged. This mode is applicable to the scenario where IP addresses need to be stable for a long time. Dynamic IP address assignment The DHCP server assigns temporary IP addresses. This mode is suitable for large-scale networks that change frequently. The zero-configuration technique is a way to automatically assign private addresses under certain conditions, ensuring that computers can continue to communicate even if there is no formal IP address assignment. Different IP address assignment modes are applicable to different network environments and requirements. Selecting the most appropriate mode is critical to network stability and security.