Configuration and application of DHCP service under RHEL

Article Title: configuration and application of DHCP service under RHEL. Linux is a technology channel of the IT lab in China. Includes desktop applications, Linux system management, kernel research, embedded systems, open source, and other basic classification I. Introduction to DHCP services
　
DHCP is based on the customer/Server mode. When the DHCP Client is started, it automatically communicates with the DHCP server. The DHCP server provides the DHCP client with a service that automatically allocates IP addresses. A server installed with the DHCP service software is called a DHCP server, and a client with the DHCP function enabled is called a DHCP client. The DHCP server provides services for the DHCP client in the form of address lease. There are two ways for the DHCP server.
　
1. Limited lease period
　
2. permanent lease
　
Ii. Working Principles of the DHCP service
　
1. Request a new IP address from the DHCP server
　
(1) DHCPDISCOVER (DHCP discovery)
　
(2) DHCPOFFER (provided by DHCP)
　
(3) DHCPREQUEST (DHCP request)
　
(4) DHCPACK (DHCP confirmation)
　
2. Update the IP address lease
　
① When the IP address of the DHCP Client reaches half of the lease period, it will send a new DHCPREQUEST to the DHCP server. if the server does not reject the request after receiving the information, it will send a DHCPACK message. When the DHCP client receives the response, it starts a new lease period.
　
② When either of the following two special cases occurs during the renewal of an IP address, additional processing is required.
　
When the DHCP Client restarts
　
When the IP address lease period exceeds half but the renewal fails
　
Iii. DHCP Service Installation
　
Red Hat Enterprise Linux installer does not install the DHCP service by default. Run the following command to check whether the system has installed the DHCP service or to check which version has been installed.
　
Rpm-q dhcp
　
If the DHCP service is not installed. If you need to install now, you can put the 3rd installation disks of Red Hat Enterprise Linux 5 into the optical drive, load the optical drive, find the RPM installation package file dhcp-3.0.5-3.el5.i386.rpm of the DHCP service under the Server Directory of the disc, then run the following command to install the DHCP service.
　
Rpm-ivh/mnt/Server/dhcp-3.0.5-3.el5.i386.rpm
　
Iv. DHCP service configuration
　
The format of the DHCP configuration file dhcpd. conf is as follows:
　
Options/parameters # these options/parameters are globally valid
　
Statement {
　
Option/parameter # these options/parameters are partially valid
　
5. Start and Stop The DHCP Service
　
1. Start the DHCP service
　
/Etc/init. d/dhcpd start
　
2. Stop the DHCP service.
　
/Etc/init. d/dhcpd stop
　
3. Restart the DHCP service.
　
/Etc/init. d/dhcpd restart