配置文件详解

[root@baism ~]# cat /etc/dhcp/dhcpd.conf

# #号代表注释

# 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;

#租约设置，默认租约为600s

default-lease-time 600;

#租约设置，最大租约为7200s，当客户端未请求明确的租约时间。

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;

}