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