DHCP配置文件详解

默认情况下，dhcp服务并没有提供配置文件，只是给提供了一个demo，存放在/usr/share/doc/dhcp*/自录下.我们将demo文件拷贝到/etc/dhcp目录下，并且命名为dhcpd.conf

租约地址路径：cat /var/lib/dhcpd/dhcpd.leases

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;

加果该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 {
}

默认启动DHCP需要一个本地网段

subnet 192.168.10.0 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.

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.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.

指定物理MAC地址获取固定IP
host fantasia {

  物理地址
  hardware ethernet 08:00:07:26:c0:a5;

  需要获取的固定IP
  fixed-address fantasia.fugue.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;
  }
}

案例一：作用域subnet和保留地址host

option domain-name "example.org";
option domain-name-servers 114.114.114.114;
default-lease-time 7200;
max-lease-time 10800;
authoritative;log-facility local7;subnet 192.168.10.0 netmask 255.255.255.0 {range 192.168.10.150 192.168.10.200;option domain-name-servers 114.114.114.114;option routers 192.168.10.1;option broadcast-address 192.168.10.255;default-lease-time 7200;max-lease-time 10800;
}host fantasia {hardware ethernet 00:0c:29:b2:f6:68;fixed-address 192.168.10.199;
}

案列二：超级作用域shared-network，可以将多个网段绑定在一起分配IP

option domain-name "example.org";
option domain-name-servers 8.8.8.8;
default-lease-time 7200;
max-lease-time 10800;
authoritative;log-facility local7;shared-network supper {
subnet 192.168.10.0 netmask 255.255.255.0 {range 192.168.10.188 192.168.10.188;option routers 192.168.10.254;
}
subnet 192.168.11.0 netmask 255.255.255.0 {range 192.168.11.188 192.168.11.188;option routers 192.168.11.254;
}
}