場景：用路由器模擬PC以及DHCP_SERVER，DHCP_CLIENT與DHCP_SERVER不在同一網段。DHCP_CLIENT會廣播DHCP_DISCOVER包發現DHCP_SERVER,由於不在同一網段而且路由器默認不轉發廣播包，所以要配置DHCP_RELAY幫忙轉發廣播包到DHCP_SERVER。
操作步驟：
步驟一：按照拓撲搭建實驗環境
步驟二：用路由器模擬PC，關閉路由功能並將接口配置爲動態獲取IP
PC(config)#no iprouting //關閉路由功能
PC(config)#intf0/0
PC(config-if)#ipaddress dhcp //將接口配置爲動態獲取IP
步驟三：在DHCP_SERVER配置接口地址，DHCP地址池以及租期等信息
DHCP_SERVER(config)#intf1/0
DHCP_SERVER(config-if)#ipadd 172.16.10.254 255.255.255.0
DHCP_SERVER(config-if)#nosh
DHCP_SERVER(config)#ipdhcp pool dhcp_pool_1 // 配置DHCP的地址池名字
DHCP_SERVER(dhcp-config)#network192.168.10.0 255.255.255.0 // 配置DHCP地址範圍
DHCP_SERVER(dhcp-config)#default-router192.168.10.254 //配置分配給主機的網關
DHCP_SERVER(dhcp-config)#lease0 8 0 //租期爲0天8小時0分鐘
DHCP_SERVER(dhcp-config)#ex
DHCP_SERVER(config)#ipdhcp excluded-address 192.168.10.250 192.168.10.254 //地址池中
需要排除的地址
DHCP_SERVER(config)#iproute 0.0.0.0 0.0.0.0 f1/0 //配置默認路由
步驟四：配置DHCP中繼
DHCP_RELAY(config)#intf0/0
DHCP_RELAY(config-if)#ipadd 192.168.10.254 255.255.255.0
DHCP_RELAY(config-if)#nosh
DHCP_RELAY(config-if)#iphelper-address 172.16.10.254
DHCP_RELAY(config)#intf1/0
DHCP_RELAY(config-if)#ipadd 172.16.10.1 255.255.255.0
DHCP_RELAY(config-if)#nosh
步驟五：使用Wireshark，觀察DHCP中繼的過程
步驟六：查看接口地址獲取情況
PC#sh ip int b
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.10.1 YES DHCP up up
FastEthernet1/0 unassigned YES unset administratively down down
配置文件
------------------------------------------------------------------------------
PC#sh run
!
hostname PC
!
no ip routing
!
!
……
!
!
interfaceFastEthernet0/0
ip address dhcp
no ip route-cache
duplex auto
speed auto
!
interfaceFastEthernet1/0
no ip address
no ip route-cache
shutdown
duplex auto
speed auto
!
!
……
!
line con 0
line aux 0
line vty 0 4
!
!
end
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DHCP_RELAY#sh run
Buildingconfiguration...
Currentconfiguration : 628 bytes
!
version 12.4
!
hostname DHCP_RELAY
!
!
!
interfaceFastEthernet0/0
ip address 192.168.10.254 255.255.255.0
ip helper-address 172.16.10.254
duplex auto
speed auto
!
interfaceFastEthernet1/0
ip address 172.16.10.1 255.255.255.0
duplex auto
speed auto
!
……
!
line con 0
line aux 0
line vty 0 4
!
!
end
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DHCP_SERVER#sh run
Buildingconfiguration...
!
hostname DHCP_SERVER
!
!
!
ip cef
no ip dhcp use vrfconnected
ip dhcpexcluded-address 192.168.10.250 192.168.10.254
!
ip dhcp pooldhcp_pool_1
network 192.168.10.0 255.255.255.0
default-router 192.168.10.254
lease 0 8
!
!
!
interfaceFastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interfaceFastEthernet1/0
ip address 172.16.10.254 255.255.255.0
duplex auto
speed auto
!
!
ip route 0.0.0.00.0.0.0 FastEthernet1/0
!
!
!
line con 0
line aux 0
line vty 0 4
!
!
end
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