DHCP for Linux network settings

DHCP overview and principle

For DHCP (Dynamic Host Configuration Protocol) details, please refer to the previous blog

Configuration command steps in CentOS7 environment

Configure DHCP server

yum install -y dhcp     #安装DHCP

cd /etc/dhcp/
ls
less dhcpd.conf         #查看配置文件，发现模板路径

cd /usr/share/doc/dhcp-4.2.5/
ls
less dhcpd.conf.example #查看模板

cp /usr/share/doc/dhcp-4.2.5/dhcpd.conf.example /etc/dhcp/dhcpd.conf #复制模板并编辑

Here I did not configure the local yum source, so I used the RPM installation

Set global configuration parameters

vim /etc/dhcp/dhcpd.conf
default-lease-time 21600; 									#默认租约为 6 小时，单位为秒
max-lease-time 43200; 										#最大租约为 12 小时，单位为秒
option domain-name "benet.com"; 							#指定默认域名
option domain-name-servers 202.106.0.20, 202.106.148.1; 	#指定 DNS 服务器地址
ddns-update-style none; 									#禁用 DNS 动态更新

#subnet网段声明（作用于整个子网段，部分配置参数优先级高于全局配置参数）
subnet 192.168.100.0 netmask 255.255.255.0 {			#声明要分配的网段地址
  range 192.168.100.10 192.168.100.20;				#设置地址池
  option routers 192.168.100.254;					#指定默认网关地址
}

subnet 192.168.10.0 netmask 255.255.255.0 {
  range 192.168.10.100 192.168.1.200;
  option routers 192.168.10.254;
}

subnet 192.168.20.0 netmask 255.255.255.0 {
  ran
  
  ge 192.168.20.220 192.168.20.230;
  option routers 192.168.20.254;
}

#host主机声明（给单机分配固定的 IP 地址）
host hostname {										#指定需要分配固定 IP地址的客户机名称
  hardware ethernet 00:c0:c3:22:46:81;				#指定该主机的 MAC地址
  fixed-address 192.168.4.100;						#指定保留给该主机的 IP地址
}

#后面内容可都删除

systemctl start dhcpd               #开启DHCP服务
systemctl stop firewalld            #关闭防火墙
setenforce 0                        #关闭防火墙

netstat -anpu | grep ":67"      #查询服务端口是否启动

If the DHCP service fails to start, you can view the log file
tail -f /var/log/messages

Virtual machine configuration information

Change the network card address


Change the network link mode

Use the local DHCP service to assign the IP address to the virtual machine

Change the IPV4 attribute of the adapter locally to use the following address

Configure DHCP relay in ensp

The commands here are not listed in detail, but a screenshot





is given. Method two

Linux客户端使用 DHCP 动态获取IP
#方法一：
vi /etc/sysconfig/network-scripts/ifcfg-ens33
DEVICE=ens33
ONBOOT=yes
BOOTPROTO=dhcp

ifdown ens33 ; ifup ens33

#方法二：
dhclient -d ens33


查看租约文件 
less /var/lib/dhcpd/dhcpd.lease