应对一个简单的局域网，拓扑简单：路由器–交换机–客户端。这样的结构。由于该公司要求使用DHCP方式自动获取IP地址，并且不限制上网、其他设备接入等功能。
于是，就出现了个人私自接入无线路由、WIFI放大器、随身WIFI等设备。导致正常接入的客户端无法通过DHCP获取到正确的地址，从而导致无法上网的情况。
该公司使用的路由为AR2200、交换机为5700。最早该公司配置为路由器当做DHCP服务器，交换机用于接入一个特殊的外网使用。发生DHCP服务器众多，导致地址分配错误的情况解决方法如下：
由于所有客户端通过交换机接入，所以配置交换的DHCP SNOOPING功能即可。
配置思路：交换机24口与路由器相连，所以配置一个port-group 把1-24口加入。全局开启DHCP功能、全局使能DHCP SNOOPING、在port-group内使能DHCP SNOOPING，进入24接口dhcp snooping trusted 。其中还做了vlanif1的DHCP中继功能。配置如下（不配置DHCP中继也是可以的）：
#
sysname Huawei
#
dhcp enable
#
dhcp snooping enable
#
interface Vlanif1
ip address 192.168.10.253 255.255.255.0
dhcp select relay
dhcp relay server-ip 192.168.10.254
#
interface MEth0/0/1
#
interface GigabitEthernet0/0/1
dhcp snooping enable
#
interface GigabitEthernet0/0/2
dhcp snooping enable
#
interface GigabitEthernet0/0/3
dhcp snooping enable
#
interface GigabitEthernet0/0/4
dhcp snooping enable
#
interface GigabitEthernet0/0/5
dhcp snooping enable
#
interface GigabitEthernet0/0/6
dhcp snooping enable
#
interface GigabitEthernet0/0/7
dhcp snooping enable
#
interface GigabitEthernet0/0/8
dhcp snooping enable
#
interface GigabitEthernet0/0/9
dhcp snooping enable
#
interface GigabitEthernet0/0/10
dhcp snooping enable
#
interface GigabitEthernet0/0/11
dhcp snooping enable
#
interface GigabitEthernet0/0/12
dhcp snooping enable
#
interface GigabitEthernet0/0/13
dhcp snooping enable
#
interface GigabitEthernet0/0/14
dhcp snooping enable
#
interface GigabitEthernet0/0/15
dhcp snooping enable
#
interface GigabitEthernet0/0/16
dhcp snooping enable
#
interface GigabitEthernet0/0/17
dhcp snooping enable
#
interface GigabitEthernet0/0/18
dhcp snooping enable
#
interface GigabitEthernet0/0/19
dhcp snooping enable
#
interface GigabitEthernet0/0/20
dhcp snooping enable
#
interface GigabitEthernet0/0/21
dhcp snooping enable
#
interface GigabitEthernet0/0/22
dhcp snooping enable
#
interface GigabitEthernet0/0/23
dhcp snooping enable
#
interface GigabitEthernet0/0/24
dhcp snooping enable
dhcp snooping trusted
#
port-group 1
group-member GigabitEthernet0/0/1
group-member GigabitEthernet0/0/2
group-member GigabitEthernet0/0/3
group-member GigabitEthernet0/0/4
group-member GigabitEthernet0/0/5
group-member GigabitEthernet0/0/6
group-member GigabitEthernet0/0/7
group-member GigabitEthernet0/0/8
group-member GigabitEthernet0/0/9
group-member GigabitEthernet0/0/10
group-member GigabitEthernet0/0/11
group-member GigabitEthernet0/0/12
group-member GigabitEthernet0/0/13
group-member GigabitEthernet0/0/14
group-member GigabitEthernet0/0/15
group-member GigabitEthernet0/0/16
group-member GigabitEthernet0/0/17
group-member GigabitEthernet0/0/18
group-member GigabitEthernet0/0/19
group-member GigabitEthernet0/0/20
group-member GigabitEthernet0/0/21
group-member GigabitEthernet0/0/22
group-member GigabitEthernet0/0/23
group-member GigabitEthernet0/0/24
#
return