接下来看看路由器是如何配置的： 路由器R1的配置：
R1#sh run
Building configuration... Current configuration : 908 bytes !
version 12.3
no service password-encryption !
hostname R1 ! ! ! !
interface FastEthernet0/0
ip address 192.168.20.254 255.255.255.0 duplex auto speed auto !
interface FastEthernet0/1 no ip address
duplex auto speed auto shutdown !
interface Serial0/0/0 no ip address
encapsulation frame-relay ietf !
interface Serial0/0/0.12 point-to-point ip address 192.168.3.1 255.255.255.0 frame-relay interface-dlci 102 !
interface Serial0/0/0.13 point-to-point ip address 192.168.1.1 255.255.255.0 frame-relay interface-dlci 103 !
interface Vlan1 no ip address shutdown !
router eigrp 100 network 192.168.20.0 network 192.168.1.0 network 192.168.3.0 auto-summary !
ip classless ! !
ip dhcp excluded-address 192.168.20.200 192.168.20.254 !
ip dhcp pool 51cto.com
network 192.168.20.0 255.255.255.0 default-router 192.168.20.254 dns-server 192.168.20.251 !
line con 0 line vty 0 4 login ! ! end
路由器R2的配置：
R2#sh run
Building configuration...
Current configuration : 908 bytes !
version 12.3
no service password-encryption !
hostname R2 ! ! ! !
interface FastEthernet0/0
ip address 192.168.40.254 255.255.255.0 duplex auto speed auto !
interface FastEthernet0/1 no ip address duplex auto speed auto shutdown !
interface Serial0/0/0 no ip address
encapsulation frame-relay ietf !
interface Serial0/0/0.21 point-to-point ip address 192.168.3.2 255.255.255.0 frame-relay interface-dlci 201 !
interface Serial0/0/0.23 point-to-point ip address 192.168.4.1 255.255.255.0 frame-relay interface-dlci 203 !
interface Vlan1 no ip address shutdown !
router eigrp 100
network 192.168.3.0 network 192.168.4.0 network 192.168.40.0 auto-summary
!
ip classless ! !
ip dhcp excluded-address 192.168.40.200 192.168.40.254 !
ip dhcp pool 51cto.com
network 192.168.40.0 255.255.255.0 default-router 192.168.40.254 dns-server 192.168.20.251 !
line con 0 line vty 0 4 login ! ! end
路由器R3的配置： R3#sh run
Building configuration...
Current configuration : 908 bytes !
version 12.3
no service password-encryption !
hostname R3 ! ! ! !
interface FastEthernet0/0
ip address 192.168.30.254 255.255.255.0 duplex auto speed auto !
interface FastEthernet0/1 no ip address duplex auto speed auto shutdown !
interface Serial0/0/0 no ip address
encapsulation frame-relay ietf