DHCP概述

• DHCP(Dynamic Host Configuration Protocol)i动态主机配置协议

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• DHCP是由Internet工作任务小组设计开发的，专门用于为TCP/IP网络中的计算机自动分配TCP/IP参数的协议。

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• 口使用DHCP服务的优势：
  ● 使用DHCP可以减少管理员的工作量，避免IP地址冲突，当网络更改IP地址网段时不
  ● 需要再重新配置每个用户的IP地址，提高了IP地址的利用率，方便客户端的配置。

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• 资源规划
  ● 确定需要dhcp server分配的IP地址段、掩码、网关、DNS

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• DHCP配置文件关键配置含义：
  ● subnet 192.168.200.0 netmask 255.255.255.0{ #subnet后跟子网网段，netmask后跟子网
  掩码
  ● range 192.168.200.201192.168.200.250; #分配的IP地址起止范围
  ● ·option domain-name-servers 202.106.0.20; #DNS服务器地址(多个地址用","隔开)
  ● option routers 192.168.200.2; #默认网关
  ● default-lease-time 600; #最小租约600秒
  ● max-lease-time 7200; #最大租约36000秒
  ● }

A.安装dhcp

yum install -y dhcp

B.查看配置文件

rpm -qc dhcp

C.修改配置文件

vi /etc/dhcp/dhcpd.conf

修改内容如下

subnet 192.168.122.0 netmask 255.255.255.0 {
	range 192.168.122.125 192.168.122.135; 
	option routers 192.168.3.254;
	optopm domain-name-servers 192.168.122.1;
} 
subnet 192.168.3.0 netmask 255.255.255.0 {
	range 192.168.3.125 192.168.3.135; //分配网络段
	option routers 192.168.3.254; //网关
	optopm domain-name-servers 192.168.122.1;//DNS服务器地址
} //多个网段添加多个subnet

修改好后重启dhcp服务

systemctl restart dhcpd

点击这里查看【LIUNX如何查看网关】

查看配置文件模板
more /usr/share/doc/dhcp-server/dhcpd.conf.example

模板文件内容如下

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

# option definitions common to all supported networks...
option domain-name "example.org";
option domain-name-servers ns1.example.org, ns2.example.org;

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.

subnet 10.152.187.0 netmask 255.255.255.0 {
}

# This is a very basic subnet declaration.

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.

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;
}

# 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.

host passacaglia {
  hardware ethernet 0:0:c0:5d:bd:95;
  filename "vmunix.passacaglia";
  server-name "toccata.example.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.
host fantasia {
  hardware ethernet 08:00:07:26:c0:a5;
  fixed-address fantasia.example.com;
}

# 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.

class "foo" {
  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
}

shared-network 224-29 {
  subnet 10.17.224.0 netmask 255.255.255.0 {
    option routers rtr-224.example.org;
  }
  subnet 10.0.29.0 netmask 255.255.255.0 {
    option routers rtr-29.example.org;
  }
  pool {
    allow members of "foo";
    range 10.17.224.10 10.17.224.250;
  }
  pool {
    deny members of "foo";
    range 10.0.29.10 10.0.29.230;
  }
}