CCIE实验室考试指南(1)

　　Lab 01-

　　Trouble-Shooting
　　Everything was fine before lunch:
　　Router_A
　　Router_A#sh run
　　Building configuration...
　　Current configuration:
　　!
　　version 11.2
　　no service password-encryption
　　no service udp-small-servers
　　no service tcp-small-servers
　　!
　　hostname Router_A
　　!
　　interface Ethernet0
　　ip address 172.16.4.17 255.255.255.240
　　!
　　interface Ethernet1
　　no ip address
　　shutdown
　　!
　　interface Serial0
　　ip address 10.16.0.5 255.255.255.252
　　no fair-queue
　　!
　　interface Serial1
　　ip address 10.16.1.5 255.255.255.252
　　ip rip authentication mode 0
　　!
　　router ospf 100
　　network 10.16.0.0 0.0.0.255 area 0
　　network 10.16.1.0 0.0.0.255 area 1
　　area 1 virtual-link 10.16.1.6 ...
　　message-digest-key 10 md5 Router_C
　　!
　　no ip classless
　　!
　　line con 0
　　exec-timeout 0 0
　　line aux 0
　　line vty 0 4
　　login
　　!
　　end
　　Router_A#sh ip ospf vir
　　Router_A#sh ip ospf virtual-links
　　Virtual Link OSPF_VL0 to router 10.16.1.6 is up
　　Run as demand circuit
　　DoNotAge LSA allowed.
　　Transit area 1, via interface Serial1, ...
　　Cost of using 64
　　Transmit Delay is 1 sec, State POINT_TO_POINT,
　　Timer intervals configured, Hello 10, Dead 40, ...
　　Wait 40, Retransmit 5
　　Hello due in 00:00:02
　　Adjacency State FULL (Hello suppressed)
　　Router_A#sh ip ospf vir
　　Router_A#sh ip ospf virtual-links
　　Virtual Link OSPF_VL0 to router 10.16.1.6 is down
　　Run as demand circuit
　　DoNotAge LSA allowed.
　　Transit area 1, Cost of using 65535
　　Transmit Delay is 1 sec, State DOWN,
　　Timer intervals configured, Hello 10, Dead 40, ...
　　Wait 40, Retransmit 5
　　Router_C

　　Router_C#sh run
　　Building configuration...
　　Current configuration:
　　version 11.3
　　no service password-encryption
　　hostname Router_C
　　interface Ethernet0
　　no ip address
　　shutdown
　　interface Serial0
　　ip address 10.16.1.6 255.255.255.252
　　no ip mroute-cache
　　no fair-queue
　　clockrate 56000
　　interface Serial1
　　ip address 10.16.2.6 255.255.255.252
　　clockrate 56000
　　router ospf 100
　　network 10.16.2.0 0.0.0.255 area 2
　　network 10.16.1.0 0.0.0.255 area 1
　　area 1 virtual-link 10.16.1.5 ...
　　message-digest-key 10 md5 Router_A
　　ip classless
　　line con 0
　　line 1 8
　　line aux 0
　　line vty 0 4
　　end
　　After lunch you have noticed a problem:
　　Router_A#sh ip ospf vir
　　Router_A#sh ip ospf virtual-links
　　Virtual Link OSPF_VL0 to router 10.16.1.6 is down
　　Run as demand circuit
　　DoNotAge LSA allowed.
　　Transit area 1, Cost of using 65535
　　Transmit Delay is 1 sec, State DOWN,
　　Timer intervals configured, Hello 10, ...
　　Dead 40, Wait 40, Retransmit 5
　　After which, you check the configurations of both routers and discover
　　that NO changes have been made!
　　What is the problem?
　　How did it happen?
　　Solution:
　　The virtual Link of Router_C does not use the correct Router ID. The
　　Router ID of Router_A is 172.16.4.17
　　Why was the virtual link UP before lunch?
　　The router ID, by default, will be the highest IP address configured.
　　Before lunch Router_A had an ID that was NOT the highest IP
　　address, in this case it must be that the Ethernet interface of Router_A
　　was configured at a later time. OSPF will not change the Router ID
　　once an ID has been established.
　　While you were at lunch you router was rebooted which changed the
　　Router ID.

　　（Written by admin，ChinaITLab BBS）