Scenario
Refer to the topology. Your company has decided to connect the main office with three other remote branch offices using point-to-point serial links.
You are required to troubleshoot and resolve OSPF neighbor adjacency issues between the main office and the routers located in the remote branch offices.
Use appropriate show commands to troubleshoot the issues and answer all four questions.
Instructions
R1 does not form an OSPF neighbor adjacency with R2. Which option would fix the issue?
A.
R1 ethernet0/1 is shutdown. Configure no shutdown command.
B.
R1 ethernet0/1 configured with a non-default OSPF hello interval of 25; configure no ip ospf hello-interval 25
C.
R2 ethernet0/1 and R3 ethernet0/0 are configured with a non-default OSPF hello interval of 25; configure no ip ospf hello-interval 25
D.
Enable OSPF for R1 ethernet0/1; configure ip ospf 1 area 0 command under ethernet0/1.
Explanation:
Here are the relevant parts of the router configs:
R1interface Loopback0description ***Loopback***ip address 192.168.1.1 255.255.255.255ip ospf 1 area 0!interface Ethernet0/0description **Connected to R1-
LAN**ip address 10.10.110.1 255.255.255.0ip ospf 1 area 0!interface Ethernet0/1description **Connected to L2SW**ip address 10.10.230.1 255.255.255.0ip ospf
hello-interval 25ip ospf 1 area 0!router ospf 1log-adjacency-changes
R2!interface Loopback0description **Loopback**ip address 192.168.2.2 255.255.255.255ip ospf 2 area 0!interface Ethernet0/0description **Connected to R2-
LAN**ip address 10.10.120.1 255.255.255.0ip ospf 2 area 0!interface Ethernet0/1description **Connected to L2SW**ip address 10.10.230.2 255.255.255.0ip ospf 2
area 0!router ospf 2log-adjacency-changes
R3username R6 password CISCO36!interface Loopback0description **Loopback**ip address 192.168.3.3 255.255.255.255ip ospf 3 area 0!interface
Ethernet0/0description **Connected to L2SW**ip address 10.10.230.3 255.255.255.0ip ospf 3 area 0!interface Serial1/0description **Connected to R4-Branch1
office**ip address 10.10.240.1 255.255.255.252encapsulation pppip ospf 3 area 0!interface Serial1/1description **Connected to R5-Branch2 office**ip address
10.10.240.5 255.255.255.252encapsulation pppip ospf hello-interval 50ip ospf 3 area 0!interface Serial1/2description **Connected to R6-Branch3 office**ip address
10.10.240.9 255.255.255.252encapsulation pppip ospf 3 area 0ppp authentication chap!router ospf 3router-id 192.168.3.3!
R4!interface Loopback0description **Loopback**ip address 192.168.4.4 255.255.255.255ip ospf 4 area 2!interface Ethernet0/0ip address 172.16.113.1
255.255.255.0ip ospf 4 area 2!interface Serial1/0description **Connected to R3-Main Branch office**ip address 10.10.240.2 255.255.255.252encapsulation pppip
ospf 4 area 2!router ospf 4log-adjacency-changes
R5!interface Loopback0description **Loopback**ip address 192.168.5.5 255.255.255.255ip ospf 5 area 0!interface Ethernet0/0ip address 172.16.114.1
255.255.255.0ip ospf 5 area 0!interface Serial1/0description **Connected to R3-Main Branch office**ip address 10.10.240.6 255.255.255.252encapsulation pppip
ospf 5 area 0!router ospf 5log-adjacency-changes
R6username R3 password CISCO36!interface Loopback0description **Loopback**ip address 192.168.6.6 255.255.255.255ip ospf 6 area 0!interface Ethernet0/0ip
address 172.16.115.1 255.255.255.0ip ospf 6 area 0!interface Serial1/0description **Connected to R3-Main Branch office**ip address 10.10.240.10
255.255.255.252encapsulation pppip ospf 6 area 0ppp authentication chap!router ospf 6router-id 192.168.3.3!
Continue checking their connected interfaces with the “show running-config” command:
R1#show running-config<<output omitted>>!interface Ethernet0/1description **Connected to L2SW**ip address 10.10.230.1 255.255.255.0ip ospf hello-interval
25ip ospf 1 area 0!<<output omitted>>
R2#show running-config<<output omitted>>!interface Ethernet0/1description **Connected to L2SW**ip address 10.10.230.2 255.255.255.0ip ospf 2 area
0!<<output omitted>>
We see the hello interval on R1 is not the same as R2 (and you can verify with the “show ip ospf interface <interface> command”) -> There is a hello and dead
interval mismatch problem. We should configure “no ip ospf hello-interval 25″ on R1.
Note: Maybe there are some versions of this question in the exam. For example there are some reports saying that Ethernet0/1 on R1 is shutdown (and this is the
correct choice in the exam). So please be careful checking the config on the routers before choosing the correct answers.