ICND2 – OSPF Hotspot

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Premium Member: You can test your knowledge with these questions first via this link.

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Note: If you are not sure about OSPF, please read my OSPF tutorial first.

Question

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Question 1

[am4show have=’p2;’]R1 is configured with the default configuration of OSPF.

From the following list of IP addresses configured on R1, which address will the OSPF process select as the router ID?

A. 192.168.0.1
B. 172.16.1.1
C. 172.16.2.1
D. 172.16.2.225

 

Answer: A[/am4show]

Explanation

The Router ID (RID) is an IP address used to identify the router and is chosen using the following sequence:

+ The highest IP address assigned to a loopback (logical) interface.
+ If a loopback interface is not defined, the highest IP address of all active router’s physical interfaces will be chosen.
+ The router ID can be manually assigned

In this case, because a loopback interface is not configured so the highest active IP address 192.168.0.1 is chosen as the router ID.

Question 2

[am4show have=’p2;’]After the network has converged, what type of messaging, if any, occurs between R3 and R4?

A. No messages are exchanged.
B. Hellos are sent every 10 seconds.
C. The full database from each router is sent every 30 seconds.
D. The routing table from each router is sent every 60 seconds.

 

Answer: B[/am4show]

Explanation

HELLO messages are used to maintain adjacent neighbors so even when the network is converged, hellos are still exchanged. On broadcast and point-to-point links, the default is 10 seconds, on NBMA the default is 30 seconds.

Although OSPF is a link-state protocol but the full database from each router is sent every 30 minutes (not seconds) -> C and D are not correct.

Question 3

[am4show have=’p2;’]To allow or prevent load balancing to network 172.16.3.0/24, which of the following commands could be used in R2? (Choose two)

A. R2(config-if)#clock rate
B. R2(config-if)#bandwidth
C. R2(config-if)#ip ospf cost
D. R2(config-if)#ip ospf priority
E. R2(config-router)#distance ospf

 

Answer: B C[/am4show]

Question 4

[am4show have=’p2;’]R1 is unable to establish an OSPF neighbor relationship with R3. What are possible reasons for this problem? (Choose two)

A. All of the routers need to be configured for backbone Area 1
B. R1 and R2 are the DR and BDR, so OSPF will not establish neighbor adjacency with R3
C. A static route has been configured from R1 to R3 and prevents the neighbor adjacency from being established.
D. The hello and dead interval timers are not set to the same values on R1 and R3
E. EIGRP is also configured on these routers with a lower administrative distance
F. R1 and R3 are configured in different areas

 

Answer: D F[/am4show]

Question 5

[am4show have=’p2;’]OSPF is configured using default classful addressing. With all routers and interfaces operational, how many networks will be in the routing table of R1 that are indicated to be learned by OSPF?

A. 2
B. 3
C. 4
D. 5
E. 6
F. 7

 

Answer: C[/am4show]

Explanation

Although OSPF is configured using default classful addressing but OSPF is a link-state routing protocol so it will always send the subnet mask of each network in their advertised routes. Therefore R1 will learn the the complete subnets. Four networks list below will be in the routing table of R1:
+ 172.16.2.64/30
+ 172.16.2.228/30
+ 172.16.2.232/30
+ 172.16.3.0/24

Note: Other networks will be learned as “Directly connected” networks (marked with letter “C”)