在linux里搭建一个dhcp服务器
注：准备一台linux服务器（此实验在Centos7系统实现）
[root@lb-1 ~]# cat /etc/centos-release
CentOS Linux release 7.9.2009 (Core)
步骤：
1.安装dhcp相关的软件包
[root@lb-1 ~]# yum install dhcp -y
2.修改配置文件，配置dhcp服务器
[root@lb-1 ~]# cd /etc/dhcp/
[root@lb-1 dhcp]# ls
dhclient.d dhclient-exit-hooks.d dhcpd6.conf dhcpd.conf scripts
[root@lb-1 dhcp]#
dhcpd.conf 是我们的主要的配置文件--》ipv4
dhcpd6.conf 是ipv6的配置文件拷贝样例文件到/etc/dhcp目录
[root@lb-1 dhcp]# cp /usr/share/doc/dhcp-4.2.5/dhcpd.conf.example /etc/dhcp/dhcpd.conf
cp：是否覆盖"/etc/dhcp/dhcpd.conf"？ y
[root@lb-1 dhcp]# vim /etc/dhcp/dhcpd.conf 编辑配置文件
#have to hack syslog.conf to complete the redirection).
log-facility local7; #指定日志类型
# A slightly different configuration for an internal subnet.
subnet 192.168.88.0 netmask 255.255.255.0 { #指定分配ip地址的网段号和子网掩码range 192.168.88.10 192.168.88.254; #指定地址池的范围，必须是上面的网段里的ipoption domain-name-servers 114.114.114.114; #指定dns服务器地址option routers 192.168.88.1; #指定网关default-lease-time 600; #最短租约时间600秒max-lease-time 7200; #最长租约时间7200秒
}注：dhcp服务器里的网关或者dns服务器配置错误，就会误导客户机上不了网
3.启动服务，调试
如果服务启动不起来，需要在接口上配置dhcp服务器里分配的网段的ip地址
[root@lb-1 network-scripts]# ip add
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00inet 127.0.0.1/8 scope host lovalid_lft forever preferred_lft foreverinet6 ::1/128 scope host valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000link/ether 00:0c:29:37:fb:39 brd ff:ff:ff:ff:ff:ffinet 192.168.88.1/24 brd 192.168.88.255 scope global noprefixroute ens33valid_lft forever preferred_lft forever[root@lb-1 network-scripts]# service dhcpd start #然后再次启动dhcp服务
Redirecting to /bin/systemctl start dhcpd.service
注：如何知道dhcp服务启动了呢？1.看进程 dhcpd2.看端口 67 udp
[root@lb-1 network-scripts]# ps aux|grep dhcpd 看进程
dhcpd 3890 0.0 0.2 105996 11964 ? Ss 11:37 0:00 /usr/sbin/dhcpd -f -cf /etc/dhcp/dhcpd.conf -user dhcpd -group dhcpd --no-pid
root 3893 0.0 0.0 112832 2292 pts/3 S+ 11:37 0:00 grep --color=auto dhcpd
[root@lb-1 network-scripts]# netstat -anplut|grep dhcp 看端口
udp 0 0 0.0.0.0:67 0.0.0.0:* 3890/dhcpd
4.测试使用
再开一台linux服务器做客户机，网卡类型选择nat模式，前面的linux dhcp服务器网卡也是nat模式
web3 这台linux服务器
需要在测试的客户机上使用dhcp动态获得ip地址
[root@web3 ~]# cd /etc/sysconfig/network-scripts/
[root@web3 network-scripts]# ls
ifcfg-ens33 ifdown-eth ifdown-post ifdown-Team ifup-aliases ifup-ipv6 ifup-post ifup-Team init.ipv6-global
ifcfg-lo ifdown-ippp ifdown-ppp ifdown-TeamPort ifup-bnep ifup-isdn ifup-ppp ifup-TeamPort network-functions
ifdown ifdown-ipv6 ifdown-routes ifdown-tunnel ifup-eth ifup-plip ifup-routes ifup-tunnel network-functions-ipv6
ifdown-bnep ifdown-isdn ifdown-sit ifup ifup-ippp ifup-plusb ifup-sit ifup-wireless
[root@web3 network-scripts]# cat ifcfg-ens33
BOOTPROTO="dhcp" #指定动态获得ip地址 dhcp表示动态获得 none表示静态配置
NAME="ens33"
DEVICE="ens33" #网卡的名字
ONBOOT="yes" #开机激活网卡[root@web3 network-scripts]# service network restart 刷新网卡服务，重新去获得ip地址[root@web3 network-scripts]# ifdown ens33;ifup ens33 刷新网卡服务，重新去获得ip地址正在确定 ens33 的 IP 信息... 完成。
注：如何修改了配置文件，需要刷新服务，生效
[root@lb-1 dhcp]# vim dhcpd.conf # have to hack syslog.conf to complete the redirection).log-facility local7;# A slightly different configuration for an internal subnet.subnet 192.168.88.0 netmask 255.255.255.0 {range 192.168.88.10 192.168.88.254;option domain-name-servers 114.114.114.114;option routers 192.168.88.88;default-lease-time 600;max-lease-time 7200;
}提醒：网关和dns服务器一定要配置正确，不然后导致客户机获得错误的网关和dns会不能上网
[root@lb-1 dhcp]# service dhcpd restart
Redirecting to /bin/systemctl restart dhcpd.service