1. area 0 区域要求有区域MD5认证，密码是net。2. area 3 作为NSSA区域，在R6上重发布还回口到到OSPF区域。3. area 3 只能看到默认路由。4. R1、R4作为DR，全网无BDR。5. R1、R2、R3之间点到多点子接口的模式。6. area 1 作为stub区域，只看到默认路由。7. R5-R6之间的链路使用MD5的链路认证。R1R1#show runBuilding configuration.Current configuration : 1300 bytes!version 12.4service timestamps debug datetime msecservice timestamps log datetime msecno service password-encryption!hostname R1!boot-start-markerboot-end-marker!no aaa new-modelmemory-size iomem 5!ip cefno ip domain lookup! ! !interface Loopback0 ip address 1.1.1.1 255.255.255.0! interface Tunnel1 ip address 51.1.1.1 255.255.255.0 shutdown!interface Serial0/0 ip address 15.1.1.1 255.255.255.0 serial restart-delay 0!interface Serial0/1 ip address 123.1.1.1 255.255.255.0 encapsulation frame-relay ip ospf message-digest-key 1 md5 net ip ospf network point-to-multipoint serial restart-delay 0!interface Serial0/2 no ip address shutdown serial restart-delay 0!interface Serial0/3 no ip address shutdown serial restart-delay 0!router ospf 110 router-id 91.1.1.1 log-adjacency-changes area 0 authentication message-digest area 2 virtual-link 95.5.5.5 network 1.1.1.0 0.0.0.255 area 0 network 15.1.1.0 0.0.0.255 area 2 network 51.1.1.0 0.0.0.255 area 2 network 123.1.1.0 0.0.0.255 area 0 neighbor 93.3.3.3 neighbor 92.2.2.2!no ip http serverno ip http secure-server!control-plane!line con 0 exec-timeout 0 0 logging synchronousline aux 0line vty 0 4!endR2R2#SHOW RUNBuilding configuration.Current configuration : 1404 bytes!version 12.4service timestamps debug datetime msecservice timestamps log datetime msecno service password-encryption!hostname R2!boot-start-markerboot-end-marker!no aaa new-modelmemory-size iomem 5!ip cefno ip domain lookup! ! !interface Loopback0 ip address 2.2.2.2 255.255.255.0! interface Ethernet0/0 no ip address shutdown half-duplex!interface Ethernet0/1 ip address 24.1.1.2 255.255.255.0 half-duplex!interface Ethernet0/2 no ip address shutdown half-duplex!interface Ethernet0/3 no ip address shutdown half-duplex!interface Serial1/0 no ip address shutdown serial restart-delay 0!interface Serial1/1 no ip address shutdown serial restart-delay 0!interface Serial1/2 ip address 123.1.1.2 255.255.255.0 encapsulation frame-relay ip ospf message-digest-key 1 md5 net ip ospf network point-to-multipoint serial restart-delay 0!interface Serial1/3 no ip address shutdown serial restart-delay 0!router ospf 110 router-id 92.2.2.2 log-adjacency-changes area 0 authentication message-digest area 1 stub no-summary network 2.2.2.0 0.0.0.255 area 0 network 24.1.1.0 0.0.0.255 area 1 network 123.1.1.0 0.0.0.255 area 0!no ip http serverno ip http secure-server!control-plane! line con 0 exec-timeout 0 0 logging synchronousline aux 0line vty 0 4!endR3SHOW RUNBuilding configuration.Current configuration : 1404 bytes!version 12.4service timestamps debug datetime msecservice timestamps log datetime msecno service password-encryption!hostname R3!boot-start-markerboot-end-marker!no aaa new-modelmemory-size iomem 5!ip cefno ip domain lookup! ! !interface Loopback0 ip address 3.3.3.3 255.255.255.0! interface Ethernet0/0 no ip address shutdown half-duplex!interface Ethernet0/1 ip address 34.1.1.3 255.255.255.0 half-duplex!interface Ethernet0/2 no ip address shutdown half-duplex!interface Ethernet0/3 no ip address shutdown half-duplex!interface Serial1/0 no ip address shutdown serial restart-delay 0!interface Serial1/1 no ip address shutdown serial restart-delay 0!interface Serial1/2 no ip address shutdown serial restart-delay 0!interface Serial1/3 ip address 123.1.1.3 255.255.255.0 encapsulation frame-relay ip ospf message-digest-key 1 md5 net ip ospf network point-to-multipoint serial restart-delay 0!router ospf 110 router-id 93.3.3.3 log-adjacency-changes area 0 authentication message-digest area 1 stub no-summary network 3.3.3.0 0.0.0.255 area 0 network 34.1.1.0 0.0.0.255 area 1 network 123.1.1.0 0.0.0.255 area 0!no ip http serverno ip http secure-server!control-plane! line con 0 exec-timeout 0 0 logging synchronousline aux 0line vty 0 4!EndR4R4#SHOW RUN