R4作为帧中继交换机 所有端口都是dce
R1，R2，R3的端口都有ip，并且关闭inverse-arp，指定frame-relay map ip 来进行选路
R1配置
interface Serial0/0
ip address 192.168.1.1 255.255.255.0
encapsulation frame-relay
serial restart-delay 0
frame-relay map ip 192.168.1.1 102 broadcast
frame-relay map ip 192.168.1.2 102 broadcast
frame-relay map ip 192.168.1.3 103 broadcast
no frame-relay inverse-arp
R2配置
interface Serial0/0
ip address 192.168.1.2 255.255.255.0
encapsulation frame-relay
serial restart-delay 0
frame-relay map ip 192.168.1.1 201 broadcast
frame-relay map ip 192.168.1.2 203 broadcast
frame-relay map ip 192.168.1.3 203 broadcast
no frame-relay inverse-arp
R3配置
interface Serial0/0
ip address 192.168.1.3 255.255.255.0
encapsulation frame-relay
serial restart-delay 0
frame-relay map ip 192.168.1.1 301 broadcast
frame-relay map ip 192.168.1.2 302 broadcast
frame-relay map ip 192.168.1.3 301 broadcast
no frame-relay inverse-arp
R4配置
interface Serial0/0
no ip address
encapsulation frame-relay
serial restart-delay 0
frame-relay intf-type dce
frame-relay route 102 interface Serial0/1 201
frame-relay route 103 interface Serial0/2 301
!
interface Serial0/1
no ip address
encapsulation frame-relay
serial restart-delay 0
frame-relay intf-type dce
frame-relay route 201 interface Serial0/0 102
frame-relay route 203 interface Serial0/2 302
!
interface Serial0/2
no ip address
encapsulation frame-relay
serial restart-delay 0
frame-relay intf-type dce
frame-relay route 301 interface Serial0/0 103
frame-relay route 302 interface Serial0/1 203
这样就可以实现全网互通了！