cat /etc/dhcp/dhcpd.conf

# DHCP服务配置文件分为全局配置和作用域配置，很好区分：subnet的就是作用域 不在subnet里面的就是全局设置。
# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

#DNS全局选项，指定DNS服务器的地址，可以是IP，也可以是域名。
# option definitions common to all supported networks...
# DNS的域名
option domain-name "example.org";

#具体的DNS服务器
option domain-name-servers ns1.example.org, ns2.example.org;

#默认租约为600s
default-lease-time 600;
#最大租约为7200s，客户机会在default-lease-time快到期时向服务器续租，如果此时客户机死机/重启，而默认租约时间到期了，服务器并不会立即回收IP地址，而是等到最大租约时间到期，客户机还没有过来续约，才会回收IP地址。
max-lease-time 7200;

#动态DNS更新方式(none:不支持；interim:互动更新模式；ad-hoc:特殊更新模式)
# Use this to enble / disable dynamic dns updates globally.
#ddns-update-style none;

#如果该DHCP服务器是本地官方DHCP就将此选项打开，避免其他DHCP服务器的干扰。
#当一个客户端试图获得一个不是该DHCP服务器分配的IP信息，DHCP将发送一个拒绝消息，而不会等待请求超时。当请求被拒绝，客户端会重新向当前DHCP发送IP请求获得新地址。保证IP是自己发出去的
#
# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
#authoritative;

# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
# 日志级别
log-facility local7;

# No service will be given on this subnet, but declaring it helps the 
# DHCP server to understand the network topology.

#作用域相关设置指令
#subnet 定义一个作用域
#netmask 定义作用域的掩码
#range 允许发放的IP范围
#option routers 指定网关地址
#option domain-name-servers 指定DNS服务器地址
#option broadcast-address 广播地址
#
#
#案例:定义一个作用域 网段为10.152.187.0 掩码为255.255.255.0
#此作用域不提供任何服务
subnet 10.152.187.0 netmask 255.255.255.0 {
}

# This is a very basic subnet declaration.

#案例:定义一个基本的作用域
#网段10.254.239.0 掩码255.255.255.224
#分发范围10.254.239.10-20
#网关为rtr-239-0-1.example.org, rtr-239-0-2.example.org
subnet 10.254.239.0 netmask 255.255.255.224 {
  range 10.254.239.10 10.254.239.20;
  option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
}

# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.
#案例:允许采用bootp协议的客户端动态获得地址
#bootp DHCP的前身
#BOOTP用于无盘工作站的局域网中，可以让无盘工作站从一个中心服务器上获得IP地址。通过BOOTP协议可以为局域网中的无盘工作站分配动态IP地址，
#这样就不需要管理员去为每个用户去设置静态IP地址。
subnet 10.254.239.32 netmask 255.255.255.224 {
  range dynamic-bootp 10.254.239.40 10.254.239.60;
  option broadcast-address 10.254.239.31;
  option routers rtr-239-32-1.example.org;
}


#案例:一个简单的作用域案例
# A slightly different configuration for an internal subnet.
subnet 10.5.5.0 netmask 255.255.255.224 {
  range 10.5.5.26 10.5.5.30;
  option domain-name-servers ns1.internal.example.org;
  option domain-name "internal.example.org";
  option routers 10.5.5.1;
  option broadcast-address 10.5.5.31;
  default-lease-time 600;
  max-lease-time 7200;
}

# Hosts which require special configuration options can be listed in
# host statements.   If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.
#
#保留地址:可以将指定的IP分发给指定的机器，根据网卡的MAC地址来做触发
#host: 启用保留。
#hardware:指定客户端的mac地址
#filename:指定文件名
#server-name:指定下一跳服务器地址
#fixed-address: 指定保留IP地址
#
#
#案例:这个案例中分发给客户端的不是IP地址信息，而是告诉客户端去找toccata.fugue.com服务器，并且下载vmunix.passacaglia文件
host passacaglia {
  hardware ethernet 0:0:c0:5d:bd:95;
  filename "vmunix.passacaglia";
  server-name "toccata.fugue.com";
}

# Fixed IP addresses can also be specified for hosts.   These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP.   Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.
# 案例:保留地址，将指定IP(fantasia.fugue.com对应的IP)分给指定客户端网卡(MAC:08:00:07:26:c0:a5)
host fantasia {
  hardware ethernet 08:00:07:26:c0:a5;
  fixed-address fantasia.fugue.com;
}

#超级作用域
#超级作用域是DHCP服务中的一种管理功能，使用超级作用域，可以将多个作用域组合为单个管理实体。
# You can declare a class of clients and then do address allocation
# based on that.   The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.


#在局域网中，可以配置策略根据各个机器的具体信息分配IP地址和其他的网络参数，客户机的具体信息：客户机能够给dhcp服务提供的信息由有两个，
#第一个就是网卡的dhcp-client-identifier（mac地址），
#第二个就是设备的vendor-class-identifier。
#管理员可以根据这两个信息给不同的机器分组。

#案例:
#按client某种类型分组DHCP,而不是按物理接口网段
#例子: SUNW 分配地址段10.17.224.0/24
# 非SUNW的主机,分配地址段10.0.29.0/24
#定义一个dhcp类:foo
#request广播中vendor-class-identifier字段对应的值前四个字节如果是"SUNW",则视合法客户端.
class "foo" {
  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
}

#定义一个超级作用域: 224-29
shared-network 224-29 {
#定义第一个作用域
  subnet 10.17.224.0 netmask 255.255.255.0 {
    option routers rtr-224.example.org;
  }
#定义第二个作用域
  subnet 10.0.29.0 netmask 255.255.255.0 {
    option routers rtr-29.example.org;
  }

#关连池,如果客户端匹配foo类，将获得该池地址
  pool {
    allow members of "foo";
    range 10.17.224.10 10.17.224.250;
  }
#关连池,如果客户端配置foo类，则拒绝获得该段地址
  pool {
    deny members of "foo";
    range 10.0.29.10 10.0.29.230;
  }
}

vim /etc/sysconfig/network-scripts/ifcfg-ens33		# 编辑网卡配置文件，设置指定IP地址

vim /etc/dhcp/dhcpd.conf			# 编辑DHCP配置文件

subnet 192.168.11.0 netmask 255.255.255.0 {
  range 192.168.11.153 192.168.11.252;
  option routers 192.168.11.254;
  option broadcast-address 192.168.11.255;
  default-lease-time 7200;
  max-lease-time 10800;
}

systemctl restart network			# 重启网络服务
systemctl start dhcpd				# 开启DHCP服务
tail -f /var/log/messages			# 查看日志
cat /var/lib/dhcpd/dhcpd.leases		# 查看租约

vim /etc/sysconfig/network-scripts/ifcfg-ens33		# 编辑网卡配置文件，设置动态获取IP地址

systemctl restart network							# 重启网络服务

ipconfig											# 查看分配的IP地址是否属于指定范围

dhclient -r ens33									# 释放获取的IP地址

dhclient -d ens33									# 将DHCP获取IP地址的进程放到前台运行