注：实验拓扑图和配置步骤参照
http://wry000.blog.51cto.com/821590/272088，感谢wry的分享。
拓扑图：
1.把路由器R4配置为帧中继交换机
frame-relay switching *配置为帧中继交换机
2.在路由器R4上配置接口的时钟频率、封装类型、lmi类型和帧中继dce端
int s0/0
no shut
clock rate 64000 *设置时钟频率
encapsulation frame-relay *封装为帧中继
frame-relay lmi-type cisco *lmi类型为cisco
frame-relay intf-type dce *帧中继的dce端
int s0/1
no shut
clock rate 64000
encapsulation frame-relay
frame-relay lmi-type cisco
frame-relay intf-type dce
int s0/2
no shut
clock rate 64000
encapsulation frame-relay
frame-relay lmi-type cisco
frame-relay intf-type dce
exit
3.在路由器R4接口上配置帧中继交换表
int s0/0
frame-relay route 102 interface Serial0/1 201
frame-relay route 104 interface Serial0/2 401
int s0/1
frame-relay route 201 interface Serial0/0 102
frame-relay route 301 interface Serial0/2 103
int s0/2
frame-relay route 401 interface Serial0/0 104
frame-relay route 103 interface Serial0/1 301
4.在R1、R2、R3路由器上配置接口IP，并封装为帧中继
R1:
R2:
R3:
encapsulation frame-relay
frame-relay lmi-type cisco
5.验证配置结果
R1:
R2:
R3:
