1. DHCP overview and principle

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Two, configuration command steps

1. Set up a DHCP configuration file

yum -y install dhcp             //首先安装dhcp
cd /etc/dhcp
less dhcpd.conf                 //看一下dhcp配置文件，大多无内容

cd /usr/share/doc/dhcp-4.2.5            //dhcp配置文件参考模板
less dhcpd.conf.example                 //查看配置文件参考模板
cp /usr/share/doc/dhcp-4.2.5/dhcpd.conf.example /etc/dhcp/dhcpd.conf   //将模板文件复制到配置文件中
vim /etc/dhcp/dhcpd.conf                //进入编辑dhcp配置文件

2. Set up the global configuration

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 "gg.com";         //指定默认域名
option domain-name-servers 8.8.8.8;     //指定 DNS 服务器地址
ddns-update-style none 		 //禁用 DNS 动态更新

3. Network segment statement

Acting on the entire subnet segment, some configuration parameters have a higher priority than the global configuration parameter
4yy Copy template, p: paste the gateway in the next line, generally .1 or .254

subnet 192.168.80.0 netmask 255.255.255.0 {
    
    	   //首先声明dhcp服务器分配网段的地址池以及子网掩码
  range 192.168.100.10 192.168.100.20;		   //设置ip地址池
  option routers 192.168.100.254;	           //指定默认网关 
}
subnet 192.168.1.0 netmask 255.255.255.0 {
    
             //其次声明其他网段以及子网
  range 192.168.1.10 192.168.1.20;                 //设置ip地址池
  option routers 192.168.1.254;                    //指定默认网关   
}
subnet 192.168.2.0 netmask 255.255.255.0 {
    
            
  range 192.168.2.10 192.168.2.20;              
  option routers 192.168.2.254;                  
}

4. Host host statement (assign a fixed IP address to a single machine)

host hostname {
    
                               //指定需要分配固定IP地址的客户机名称
  hardware ethernet  xx:xx:xx:xx:xx:xx;   //指定该主机的MAC地址
  fixed-address 192.168.71.88;           //指定保留给该主机的IP地址
}

5. Turn on the service

systemctl start dhcpd                          //开启dhcp服务
systemctl stop firewalld                       //关闭防火墙
sentenforce 0                                  //关闭防火墙
netstat -naup | grep 67                        //查看服务是否启动
tail -f /var/log/messages                      //如果启动失败，可以通过查看日志文件来排查错误

6. Instance configuration

Set up network

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<Huawei>
<Huawei>u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sysname sw2 
[sw2]user-interface console 0 
[sw2-ui-console0]idle-timeout 0 0
[sw2-ui-console0]vlan bat 10 20 100
Info: This operation may take a few seconds. Please wait for a moment...done.
[sw2]int g0/0/3
[sw2-GigabitEthernet0/0/3]p l t
[sw2-GigabitEthernet0/0/3]p t a v a
[sw2-GigabitEthernet0/0/3]int vlanif 10
[sw2-Vlanif10]ip add 192.168.1.254 24
[sw2-Vlanif10]int vlan 20
[sw2-Vlanif20]ip add 192.168.2.254 24
[sw2-Vlanif20]int vlan 100
[sw2-Vlanif100]ip add 192.168.100.254 24
[sw2-Vlanif100]
[sw2-Vlanif100]dhcp enable
Info: The operation may take a few seconds. Please wait for a moment.done.
[sw2] 
[sw2]dhcp enable
[sw2]int vlan 100 
[sw2-Vlanif100]dhcp select relay 
[sw2-Vlanif100]dhcp relay server-ip 192.168.100.20
[sw2-Vlanif100]int vlan 10
[sw2-Vlanif10]dhcp select relay
[sw2-Vlanif10]dhcp relay server-ip 192.168.100.20
[sw2-Vlanif10]int vlan 20
[sw2-Vlanif20]dhcp select relay
[sw2-Vlanif20]dhcp relay server-ip 192.168.100.20


<Huawei>
<Huawei> u t m
Info: Current terminal monitor is off.
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]user-interface console 0
[Huawei-ui-console0]idle-timeout 0 0
[Huawei-ui-console0]q
[Huawei]vlan bat 10 20 100
Info: This operation may take a few seconds. Please wait for a moment...done.
[Huawei]int e0/0/1
[Huawei-Ethernet0/0/1]p l a 
[Huawei-Ethernet0/0/1]p d v 10
[Huawei-Ethernet0/0/1]int e0/0/2
[Huawei-Ethernet0/0/2]p l a
[Huawei-Ethernet0/0/2]p d v 20
[Huawei-Ethernet0/0/2]int e0/0/3
[Huawei-Ethernet0/0/3]p l a
[Huawei-Ethernet0/0/3]p l t
[Huawei-Ethernet0/0/3]p t a v a
[Huawei-Ethernet0/0/3]int e0/0/4
[Huawei-Ethernet0/0/4]p l a
[Huawei-Ethernet0/0/4]p d v 100
[Huawei-Ethernet0/0/4]
[Huawei-Ethernet0/0/4]