實驗描述：某公司分爲一個總部和兩個分部，屬於典型的Hub-and-Spoke模式（中心-分支），總部通過ISP使用幀中繼技術與兩個分部相連
實驗拓撲：
ISP內部網絡的部署情況我們不得而知，爲了這個實驗，使用三臺路由器來模擬幀中繼交換機，下面模擬幀中繼交換機的配置不是重點，但是可以更好的理解幀中繼交換機是怎樣利用DLCI來實現包交換的
FR-1
FR1>enable
FR1#configure terminal
FR1(config)#frame-relay switching
FR1(config)#int serial 0/0
FR1(config-if)#encapsulation frame-relay
FR1(config-if)#frame-relay intf-type dce
FR1(config-if)#clock rate 64000
FR1(config-if)#frame-relay lmi-type cisco
FR1(config-if)#frame-relay route 100interface serial 0/1 101
FR1(config-if)#frame-relay route 200interface serial 0/2 201
FR1(config-if)#no shutdown
FR1(config-if)#int s0/1
FR1(config-if)#encapsulation frame-relay
FR1(config-if)#frame-relay intf-typedce
FR1(config-if)#clock rate 64000
FR1(config-if)#frame-relay lmi-typecisco
FR1(config-if)#frame-relay route 101interface serial 0/0 100
FR1(config-if)#no shutdown
FR1(config-if)#int s0/2
FR1(config-if)#encapsulationframe-relay
FR1(config-if)#frame-relay intf-typedce
FR1(config-if)#clock rate 64000
FR1(config-if)#frame-relay lmi-typecisco
FR1(config-if)#frame-relay route 201interface serial 0/0 200
FR1(config-if)#no shutdown
FR2>enable
FR2#configure terminal
FR2(config)#frame-relay switching
FR2(config)#interface s0/0
FR2(config-if)#encapsulation frame-relay
FR2(config-if)#frame-relay intf-type dce
FR2(config-if)#clock rate 64000
FR2(config-if)#frame-relay lmi-type cisco
FR2(config-if)#frame-relay route 102 interfaceserial 0/1 101
FR2(config-if)#no shutdown
FR2(config-if)#interface s0/1
FR2(config-if)#encapsulation frame-relay
FR2(config-if)#frame-relay intf-type dte
FR2(config-if)#frame-relay lmi-type cisco
FR2(config-if)#frame-relay route 101 interface serial0/0 102
FR2(config-if)#no shutdown
FR-3
FR3>enable
FR3#configure terminal
FR3(config)#frame-relay switching
FR3(config)#interface serial 0/0
FR3(config-if)#encapsulation frame-relay
FR3(config-if)#frame-relay intf-type dce
FR3(config-if)#clock rate 64000
FR3(config-if)#frame-relay lmi-type cisco
FR3(config-if)#frame-relay route 202interface serial 0/2 201
FR3(config-if)#no shutdown
FR3(config-if)#interface serial 0/2
FR3(config-if)#encapsulationframe-relay
FR3(config-if)#frame-relay intf-typedte
FR3(config-if)#frame-relay lmi-typecisco
FR3(config-if)#frame-relay route 201interface serial 0/0 202
FR3(config-if)#no shutdown
frame-relayswitching
接下來纔是我們要關心的配置，實現總部到兩個分部的連接且兩個連接屬於不同的網段，那麼就要用點到點的子接口
R1
R1>enable
R1#configure terminal
R1(config)#interface serial 0/0
R1(config-if)#encapsulation frame-relay
R1(config-if)#frame-relay lmi-type cisco
R1(config-if)#no shutdown
R1(config)#interface serial 0/0.1point-to-point
R1(config-subif)#ip address 192.168.4.1255.255.255.0
R1(config-subif)#frame-relay interface-dlci100
R1(config-fr-dlci)#interface serial 0/0.2point-to-point
R1(config-subif)#ip address 192.168.5.1255.255.255.0
R1(config-subif)#frame-relay interface-dlci200
配置內網IP和動態路由
R1(config-subif)#int e1/0
R1(config-if)#ip address 192.168.1.1255.255.255.0
R1(config-if)#ip ospf networkpoint-to-point
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#router ospf 1
R1(config-router)#network 192.168.1.0 0.0.0.255area 0
R1(config-router)#network 192.168.4.0 0.0.0.255area 0
R1(config-router)#network 192.168.5.0 0.0.0.255area 0
R2
R2>ena
R2#configureterminal
R2(config)#interface s0/0
R2(config-if)#encapsulation frame-relay
R2(config-if)#frame-relay lmi-type cisco
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface serial 0/0.1point-to-point
R2(config-subif)#ip address 192.168.4.2255.255.255.0
R2(config-subif)#frame-relay interface-dlci102
R2(config-if)#int e1/0
R2(config-if)#ip address 192.168.2.1255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#router ospf 1
R2(config-router)#network 192.168.2.0 0.0.0.255area 0
R2(config-router)#network 192.168.4.0 0.0.0.255area 0
R3
R3>enable
R3#configure terminal
R3(config)#interface serial 0/0
R3(config-if)#encapsulation frame-relay
R3(config-if)#frame-relay lmi-type cisco
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface serial 0/0.1point-to-point
R3(config-subif)#ip address 192.168.5.2255.255.255.0
R3(config-subif)#frame-relay interface-dlci202
R3(config-if)#int e1/0
R3(config-if)#ip address 192.168.3.1255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#router ospf 1
R3(config-router)#network 192.168.3.0 0.0.0.255area 0
R3(config-router)#network 192.168.5.0 0.0.0.255area 0
驗證三臺連接總部和分部的路由器上的路由信息
路由的學習可以很好的完成
接下來不妨看一下ISP的幀中繼交換機上的PVC，但這並不是我們要關心的重點，只是學習，瞭解其工作原理
可以對比拓撲看一下，幀中繼交換機對比接收報文所攜帶的DLIC值和本地的狀態表，把數據包的DLCI值更改後發往下一個幀中繼交換機
查看一下總部的PC是否能與分部的PC通信
