实验描述：某公司分为一个总部和两个分部，属于典型的Hub-and-Spoke模式（中心-分支），总部通过ISP使用帧中继技术与两个分部相连
实验拓扑：
ISP内部网络的部署情况我们不得而知，为了这个实验，使用三台路由器来模拟帧中继交换机，下面模拟帧中继交换机的配置不是重点，但是可以更好的理解帧中继交换机是怎样利用DLCI来实现包交换的
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
接下来才是我们要关心的配置，实现总部到两个分部的连接且两个连接属于不同的网段，那么就要用点到点的子接口
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
配置内网IP和动态路由
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
验证三台连接总部和分部的路由器上的路由信息
路由的学习可以很好的完成
接下来不妨看一下ISP的帧中继交换机上的PVC，但这并不是我们要关心的重点，只是学习，了解其工作原理
可以对比拓扑看一下，帧中继交换机对比接收报文所携带的DLIC值和本地的状态表，把数据包的DLCI值更改后发往下一个帧中继交换机
查看一下总部的PC是否能与分部的PC通信
