Configuration of Linux DHCP servers

DHCP overview

1 Necessity of using DHCP

On a TCP/IP network, each workstation must have a basic network configuration before it can access resources on the network, some key parameters such as IP address, subnet mask, default gateway, DNS, and so on, and may require additional information such as IP management policies. For a slightly larger network, the task of managing and maintaining the network is quite onerous. Once a computer is transferred from one subnet to another, it is necessary to reconfigure the system. For ordinary level workstation users, it is not necessary to give them permission to configure their own workstation network. If a user does not have the appropriate level of technology out of curiosity or want to learn the purpose of incorrectly changing the workstation network configuration, resulting in network failure, the consequences are self-evident. Therefore, there is a need for a mechanism for TCP/IP configuration and management from the user side to the network management side, IP centralized management. The solution is to use DHCP.

2 main functions of DHCP

The full name of DHCP is the Dynamic Host Configuration Protocol (Dynamics host Configuration Protocol), designed by the IETF (Internet Network Engineer Task Force), with detailed protocol content in RFC documents RFC2131 and rfc1541. The aim is to reduce the burden of the planning, management and maintenance of TCP/IP networks, and to address the lack of address space. The server running DHCP sets up the TCP/IP network settings, dynamically handles the configuration of the workstation IP address, uses the DHCP lease and the preset IP address, the DHCP lease provides the mechanism of automatically allocating and renting IP address securely on TCP/IP network, realizes the centralized management of IP address, There is basically no need for human intervention by network administrators. Furthermore, DHCP itself has been designed as an extension of BOOTP (Bootstrap protocol) to support diskless workstations requiring network configuration information, as well as support for systems requiring fixed IP.

How the work of DHCP works

Several DHCP nouns

Before introducing how DHCP works, explain the meaning of these nouns first:

DHCP client: A DHCP client is an Internet host that obtains network configuration parameters through DHCP, typically a workstation for ordinary users.

DHCP server: A DHCP server is an Internet host that provides network settings parameters to DHCP clients.

DHCP/BOOTP Relay Agent: A host or router that forwards DHCP messages between DHCP clients and servers.

DHCP is designed based on the client/server model, which communicates between DHCP clients and DHCP servers by sending and receiving DHCP messages.

Format for DHCP messages:

DHCP messages are formatted in the same way as BOOTP messages, which can be designed to enhance BOOTP server tools while providing BOOTP and DHCP two customer services. In addition, a BOOTP relay agent can be used to forward DHCP requests across subnets.