linuxdhcp服务器分配（Linux实现DHCP服务器的搭建）

systemctl start dhcpd

cp  /usr/share/doc/dhcp-4.2.5/dhcpd.conf.example /etc/dhcp/dhcpd.conf

  7 option domain-name "server.com"; 
      ##域名:参见/etc/resolv.conf
  8 option domain-name-servers 172.25.10.254;
      ##指定dns服务器，多台用逗号隔开。
 30 subnet 172.25.10.0 netmask 255.255.255.0 {
      ##指定子网络及子网掩码
 31   range 172.25.10.10 172.25.10.20;
      ##指定IP范围
 32   option routers 172.25.10.254;
 ##指定默认网关
 33 }
 34#### 删除27,28行，34行及以后

DEVICE=eth0
BOOTPROTO=dhcp
###关键部位为dhcp
ONBOOT=yes

systemctl restart network
###在本次试验，我遇到了如下问题：执行该命令报错，无法通过DHCP服务器获得ip,解决思路为：DHCP通常是用于局域网内的一个通信协议，它主要通过客户端发送广播数据包给整个物理网段内的所有主机，若局域网内有DHCP服务器时，才会响应客户端的ip参数要求。所以DHCP服务器与客户端应该在同一个物理网段内。整个DHCP数据包在服务器与客户端间的交互情况如下图(1)：
###所以我猜测是防火墙阻止了数据包的传送
###我采取的解决方法是：
两台虚拟机均执行命令：
firewall-cmd --permanent --add-service=dhcp
firewall-cmd --reload 
查看dhcp是否通行：
firewall-cmd --list-all
重启虚拟机后问题解决。

# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

# option definitions common to all supported networks...
option domain-name "example.org";
option domain-name-servers 192.168.0.199;

default-lease-time 600;
max-lease-time 7200;

# Use this to enble / disable dynamic dns updates globally.
#ddns-update-style none;

# 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).
log-facility local7;

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


# This is a very basic subnet declaration.

subnet 192.168.0.0 netmask 255.255.255.0 {
  range 192.168.0.10 192.168.0.20;
  option routers 192.168.0.199;
}