Case study.
 
Some notices from above configuration:
+The OSPF network type between R2&R3 is non broadcast.
Q1: Show ip ospf database -
Q2: Show ip ospf interface serial 1/0
Q3: Show ip ospf -
Q4: Show ip route -
You have been asked to evaluate an OSPF network and to answer questions a customer has about its operation. Note: You are not allowed to use the show command. running-config
 
Although in this sim we are not allowed to use "show running-config" command but we post the configuration here so that you can understand more about the topology.
R1 -
interface Loopback0
ip address 1.1.1.1 255.255.255.255
no shut
interface Serial0/0
ip address 192.168.13.1 255.255.255.0
ip ospf network non-broadcast
no shut
router ospf 1
network 192.168.13.0 0.0.0.255 area 0
network 1.1.1.1 0.0.0.0 area 0
_______________________________________
R2 -
interface Loopback 0
ip address 2.2.2.2 255.255.255.255
no shut
interface S0/0
ip address 192.168.23.2 255.255.255.0
ip ospf network non-broadcast
no shut
router ospf 1
network 192.168.23.0 0.0.0.255 area 0
network 2.2.2.2 0.0.0.0 area 0
neighbor 192.168.23.3
_________________________________________________
R3 -
interface Loopback 0
ip address 3.3.3.3 255.255.255.255
no shut
interface fa0/0
ip address 192.168.34.3 255.255.255.0
no shut
interface S0/1
ip address 192.168.23.3 255.255.255.0
ip ospf network non-broadcast
no shut
interface S0/0
ip address 192.168.13.3 255.255.255.0
ip ospf network non-broadcast
no shut
router ospf 1
network 192.168.13.0 0.0.0.255 area 0
network 192.168.23.0 0.0.0.255 area 0
network 192.168.34.0 0.0.0.255 area 1
network 3.3.3.3 0.0.0.0 area 0
area 1 virtual-link 4.4.4.4
neighbor 192.168.23.2
_______________________________________________________________
R4 -
interface Loopback 0
ip address 4.4.4.4 255.255.255.255
interface FastEthernet0/0
ip address 192.168.34.4 255.255.255.0
interface Fa0/1
ip address 192.168.45.4 255.255.255.0
no shut
interface Fa1/0
ip address 192.168.46.4 255.255.255.0
no shut
router ospf 1
network 192.168.34.0 0.0.0.255 area 1
network 192.168.45.0 0.0.0.255 area 2
network 192.168.46.0 0.0.0.255 area 3
network 4.4.4.4 0.0.0.0 area 1
area 1 virtual-link 3.3.3.3
area 2 nssa
area 3 stub no-summary
_________________________________________________________________
R5 -
interface Loopback0
ip address 5.5.5.5 255.255.255.255
interface Loopback1
ip address 5.5.1.1 255.255.255.255
interface Loopback2
ip address 5.5.2.1 255.255.255.255
interface Loopback3
ip address 5.5.3.1 255.255.255.255
interface Loopback4
ip address 5.5.4.1 255.255.255.255
no shut
interface Fa0/0
ip address 192.168.45.5 255.255.255.0
no shut
router ospf 1
network 192.168.45.0 0.0.0.255 area 2
network 5.5.0.0 0.0.255.255 area 2
area 2 nssa
_______________________________________________
R6 -
interface Fa0/0
ip address 192.168.46.6 255.255.255.0
no shut
interface Loopback 0
ip address 6.6.6.6 255.255.255.255
no shut
router ospf 1
network 192.168.46.0 0.0.0.255 area 3
network 6.6.6.6 0.0.0.0 area 3
area 3 stub
Which of the following statements is true about the serial links that terminate in R3?

A. The R1-R3 link needs the neighbor command for the adjacency to stay up

B. The R2-R3 link OSPF timer values are 30, 120, 120

C. The R1-R3 link OSPF timer values should be 10,40,40

D. R3 is responsible for flooding LSUs to all the routers on the network.








 

Suggested Answer: B

Check the Serial1/0 interface of R3 which is connected to R2 with the "show ip ospf interface serial 1/0" command:
 <img src="https://www.examtopics.com/assets/media/exam-media/02670/0044600001.png" alt="Reference Image" />
There are two things we should notice from the output above:
+ The "network type" connection between R2-R3 is "NON_BROADCAST" (usually we have "BROADCAST"). OSPF neighbors are discovered using multicast
Hello packets. In non broadcast environment, multicast (and broadcast) messages are not allowed so OSPF neighborship cannot be formed automatically.
Therefore we have to establish OSPF neighborship manually by using "neighbor " command under OSPF process (OSPF will send unicast Hello message to this address). For example on R2 we have to use these commands: router ospf 1 neighbor 192.168.23.3
And on R3:
router ospf 1
neighbor 192.168.23.2
+ For non broadcast environment the default Hello timer is 30 seconds; Dead timer (time to wait before declaring a neighbor dead) is 120 seconds and Wait timer
(causes the interface to exit out of the wait period and select a DR on a broadcast network. This timer is always equal to the dead timer interval) is 120 seconds. In the output we also see the default timers for non broadcast network.

This question is in 300-101 Cisco Implementing Cisco IP Routing (ROUTE) Exam
For getting Cisco Certified Network Professional (CCNP) Routing and Switching Certificate




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