Linux操作系统下单网卡分配多网段的方法

来源：赛迪网    作者：korn

如果你的DHCP服务只监听一个网卡，这个网卡绑定多个IP，比如 192.168.0.1,192.168.1.1

　　而想要DHCP同时可以分配2个网段的IP请求，像下面这样的配置(dhcpd.conf)

subnet 192.168.0.0 netmask 255.255.255.0 {
range 192.168.0.100 192.168.0.200 ;
option routers 192.168.0.1 ;
option domain-name-servers 192.168.2.1,202.112.31.58 ;
}
subnet 192.168.1.0 netmask 255.255.255.0 {
range 192.168.1.100 192.168.2.200 ;
option routers 192.168.1.1 ;
option domain-name-servers 192.168.2.1,202.112.31.58 ;
}

　　DHCP 服务是启动不起来的，会提示 Interface eth0 matches multiple shared networks

　　此时只要把上面的配置放到 shared-network中就行了，像下面这样：

shared-network network_tag {
...
}

　　一般情况下，单网卡DHCP服务器分配多网段主要用于VLAN场合，当然DHCP服务器本生也要能支持VLAN，linux内核已经对802.1q支持了，只需要下载vconfig软件包进行配置下就行了，具体就不说了，网上很多关于这样的帖子。下面是一个典型的应用例子：

Client Area A -----Switch -----VLAN 1-----------,
Client Area B -----Switch -----VLAN 2-------- Switch ----Trunk --- DHCP Server

Client Area C -----Switch -----VLAN 3-----------'

　　DHCP 服务器在分配IP时，会根据 DHCP 请求数据包中VLAN 的标识来决定分配哪个网段的IP，这样可以保证同一VLAN的用户分配的IP始终是同一网段的，当然交换机必须得支持VLAN和DHCP relay功能

　　我的配置文件（Ubuntu下）

1：/etc/network/interface

auto eth0
iface eth0 inet static
address 192.168.0.1
netmask 255.255.255.0
network 192.168.0.0
broadcast 192.168.0.255
gateway 192.168.0.254
auto eth0:0
iface eth0:0 inet static
address 192.168.1.1
netmask 255.255.255.0
network 192.168.0.0
broadcast 192.168.0.255
gateway 192.168.1.254

2：/etc/dhcpd.conf

default-lease-time 21600;
max-lease-time 21600;
option domain-name-servers 222.92.109.230,61.177.7.1,61.147.37.1;
option domain-name "glfsoft.com";

shared-network network_tag {
subnet 192.168.0.0 netmask 255.255.255.0 {
# range 192.168.0.21 192.168.0.31;
option broadcast-address 192.168.0.255;
option subnet-mask 255.255.255.0;
option routers 192.168.0.254;
next-server 192.168.0.254;
host kook {
hardware ethernet 00:1A:4B:58:36:9D;
fixed-address 192.168.0.9;
}
}
subnet 192.168.1.0 netmask 255.255.255.0 {
# range 192.168.1.21 192.168.1.31;
option broadcast-address 192.168.1.255;
option subnet-mask 255.255.255.0;
option routers 192.168.1.254;
next-server 192.168.1.254;
host kook2 {
hardware ethernet 00:E0:A0:11:BE:21;

fixed-address 192.168.1.9;
}
}
}