DHCP的配置与分析
由路由R1，R2，R3，把R1当作DHCP服务器，让R2的R3从它上面自动获得IP地址，分析一下为什么他们获得的不一样（不是R3获得的不是R1地址池中的地址）。
R1上DHCP服务器的配置
Router(config)#host R1
R1(config)#no ip do
R1(config)#no ip domain-lo
R1(config)#service dhcp 定为DHCP服务器
R1(config)#no ip dhcp conflict logging 没有地址冲突
R1(config)#ip dhcp excluded-address 12.1.1.1 排除一个地址
R1(config)#ip dhcp pool cisco 做一个地址池
R1(dhcp-config)#network 12.1.1.0 255.255.255.0 地址为
R1(dhcp-config)#default-router 12.1.1.1 默认路由
R1(dhcp-config)#dns-server 192.168.1.1 DNS服务器地址
R1(dhcp-config)#lease 1 租用期限
R1(dhcp-config)#int fa0/0
R1(config-if)#ip add 12.1.1.1 255.255.255.0
R1(config-if)#no shu
R2上的配置：
Router(config)#host R2
R2(config)#no ip domain-lo
R2(config)#int fa0/0
R2(config-if)#ip add dhcp host R1 从R1上的DHCP服务器上获得IP地址
R2(config-if)#no shu
R2(config-if)#end
R2#show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 12.1.1.2 YES DHCP up up
Serial1/0 unassigned YES unset administratively down down
Serial1/1 unassigned YES unset administratively down down
Serial1/2 unassigned YES unset administratively down down
Serial1/3 unassigned YES unset administratively down down
R3上的配置
Router(config)#host R3
R3(config)#no ip domain-lo
R3(config)#int fa0/0
R3(config-if)#ip address dhcp （从DNS服务器上获得地址了）
R3(config-if)#no shu
R3(config-if)#end
R3#show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.1.105 YES DHCP up up
Serial1/0 unassigned YES unset administratively down down
Serial1/1 unassigned YES unset administratively down down
Serial1/2 unassigned YES unset administratively down down
Serial1/3 unassigned YES unset administratively down down
