一.DHCP总览
DHCP:动态主机配置协议，通过dhcpd实施，为dhcpd和bootp ipv4，ipv6客户端提供服务。
二.DHCP协议工作原理
第一步：客户端请求IP地址-----发送一个DHCPDISCOVER广播包
第二步：DHCP SERVER响应请求----广播一个DHCPOFFER包
第三步：客户端选择IP地址----广播一个DHCPREQUEST包
第四步：服务器确认IP租约----发送一个DHCPACK包
三.服务简介：DHCP
类型：system V 管理的服务
软件名：dhcp
守护进程：/usr/sbin/dhcpd
脚本：/etc/init.d/dhcpd
端口：67(bootps),68(bootpc)
配置文件：/etc/dhcp/dhcpd.conf,/var/lib/dhcpd/dhcpd.leases
四.配置IPv4 DHCP服务器
第一步：安装软件包
#yum install dhcp
第二步：获取配置文件 (rpm -ql dhcp|less)
#cp /usr/share/doc/dhcp-version/dhcp.conf.sample /etc/dhcp/dhcpd.conf
第三步：按需求定义配置文件，并启动服务
1./etc/init.d/dhcpd start
2.chkconfig dhcpd on
五.DHCP配置文件模版
#必须至少要定义一个subnet块
subnet 192.168.177.0 netmask 255.255.255.0 {
range 192.168.177.26 192.168.177.30;
option domain-name-servers ns1.internal.example.org;
option domain-name "internal.example.org";
option routers 192.168.177.128;
option broadcast-address 192.168.177.255;
default-lease-time 600;
max-lease-time 7200;
}
全部的配置文件如下：
# 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.
# This is a very basic subnet declaration.
# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.
# A slightly different configuration for an internal subnet.
subnet 192.168.177.0 netmask 255.255.255.0 {
range 192.168.177.26 192.168.177.30;
option domain-name-servers ns1.internal.example.org;
option domain-name "internal.example.org";
option routers 192.168.177.128;
option broadcast-address 192.168.177.255;
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.
# 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.fugue.com;
}
六.绑定IP地址
subnet 192.168.177.0 netmask 255.255.255.0 {
range 192.168.177.26 192.168.177.30;
......truncated......
}
host client1 {
hardware ethernet aa:bb:cc:dd:ee:ff;
#该地址必须是DHCP和BOOTP ranges之外的
fixed-address fantasia.fugue.com;
}
七.DHCP提供文件
subnet 192.168.177.0 netmask 255.255.255.0 {
range 192.168.177.26 192.168.177.30;
......truncated......
#指定服务器和文件的位置
next-server 192.168.0.254;#可以是DNS服务器，也可以是TFTP服务器
filename "pxelinux.0";#要使用引号
}
八.DHCP服务其他
语法检查工具：service dhcpd configtest
限制DHCP监听特定接口：修改/etc/sysconfig/dhcpd