Fix OSPF
The triangle should be running OSPF area 0 everywhere, with passive LAN interfaces, but users on all three LANs report that they can't reach the other sites. Find and fix every fault, so that every router has two FULL neighbours and every PC reaches every other PC. Keep the passive LAN interfaces.
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Solution explanation
Four faults. On R1, the passive interface was Gi0/1 (the link to R2) instead of Gi0/0 (the LAN): no hellos to R2, and hellos going out to the PCs. On R2, the link to R3 was in area 1 while R3 had it in area 0 (R3 logged a mismatched area ID). Also on R2, the LAN's network command said 192.168.20.0, which matches no interface, so PC2's LAN was never advertised (and Gi0/2 wasn't in OSPF at all, so it couldn't be passive either). On R3, Gi0/0's dead interval was 30 instead of 40, so R1 and R3 refused each other's hellos.
Show solution
[R1]
enable
show ip ospf interface brief
show ip protocols
configure terminal
router ospf 1
no passive-interface g0/1
passive-interface g0/0
end
[R2]
enable
show running-config | section router ospf
configure terminal
router ospf 1
no network 10.0.23.0 0.0.0.3 area 1
network 10.0.23.0 0.0.0.3 area 0
no network 192.168.20.0 0.0.0.255 area 0
network 192.168.2.0 0.0.0.255 area 0
end
[R3]
enable
show ip ospf interface g0/0 | include Timer
configure terminal
interface g0/0
no ip ospf dead-interval
end
show ip ospf neighbor
[PC1]
ping 192.168.2.10
ping 192.168.3.10
[PC2]
ping -c 3 192.168.3.10