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New Cisco CCNA : OSPF Multiple Choice Questions.

Updated Sept 2013
Question 1:
Which of the following statements below best describe the process identifier that is used to run OSPF on a router? (Choose two)
A - It is an optional parameter required only if multiple OSPF processes are running on the router
B - It is locally significant
C - It is needed to identify a unique instance of an OSPF database
D - All routers in the same OSPF area must have the same process ID if they are to exchange routing information
 

Answer: B C

Explanation:

The process ID is the ID of the OSPF process to which the interface belongs. The process ID is local to the router, and two OSPF neighboring routers can have different OSPF process IDs. (This does not apply to Enhanced Interior Gateway Routing Protocol [EIGRP], in which the routers need to be in the same autonomous system). Cisco IOS Software can run multiple OSPF processes on the same router, and the process ID merely distinguishes one process from another. The process ID should be a positive integer
 
Question 2:

Why R1 can't establish an OSPF neighbor relationship with R3 according to the following graphic? (Choose two)

OSPF Multiple choice questions
 

A - Configure EIGRP on these routers with a lower administrative distance
B - All routers should be configured for backbone Area 1
C - R1 and R3 have been configured in different areas
D - The hello and dead interval timers are not configured the same values on R1 and R3

Answer: C D

Explanation:

OSPF is a link state routin protocol, It establishes and maintains neighbor relationships so as to exchange routing updates with other routers. OSPF neighbor relationship table is called an adjacency database . Provided that OSPF is configured correctly, OSPF forms neighbor relationships only with the routers directly connected to it. The routers that it forms a neighbor relationship with must be in the same area as the interface with which it is using to form a neighbor relationship.

A neighbor that is discovered dynamically through reception of HELLO packets can fall back to a down state if it is being deleted, for example when OSPF does not receive HELLO packets from the neighbor for period of time longer than the Dead timer interval. Therefore, the down state is transient for such neighbors; they will either advance to higher states or be completely deleted from the table of known neighbors.

Therefore, for relationship to be established among OSPF neighboring routers, the following must be correctly configured:

i. Area ID (Area 0 as seen above)

ii. Hello and dead intervals

iii. Authentication password
 

Question 3:

Which items are correct about the routing protocol OSPF? (Choose three)

A - Support VLSM
B - Increase routing overhead on the network
C - Confine network instability to one area of the network
D - Allow extensive control of routing updates

Answer: A C D


Brief explanation:

Ospf features:

i. Can use VLSM

ii. Converges quickly

iii. Uses the concept of areas which helps for route summarization

iv. Allows authentication

v. Uses Dijkstra’s algorithm (SPF Algorithm)

vi. Reduces the usage of bandwidth (BW) by sending triggered updates to announce changes in the network

vii. Sending periodic updates 30min interval. Uses short Hello messages on a short regular interval, with the absence of hello messages indicating that a neighbor is no longer reachable.

Finally, to confine network instability to one area of the network, OSPF uses router ID or a 32-bit IP address selected at the beginning of the OSPF process. The highest IP address configured on the router is the router ID. If a loopback address is configured, then it is the router ID. In case of multiple loopback addresses, the highest loopback address is the router ID. Once the router ID is elected it doesn't change unless the IP address is removed or OSPF restarts.

Question 4:

Which three features are of OSPF routing protocol? (Choose three)

A - Converge quickly
B - OSPF is a classful routing protocol
C - Identify the best route by use of cost
D - Before exchanging routing information, OSPF routers find out neighbors

Answer: A C D

Explanation as above.

Question 5:

OSPF routing uses the concept of areas. What are the characteristics of OSPF areas? (Chose three)

A - Each OSPF area requires a loopback interface to be configured
B - Areas may be assigned any number from 0 to 65535
C - Area 0 is called the backbone area
D - Hierarchical OSPF networks do not require multiple areas
E - Multiple OSPF areas must connect to area 0
F - Single area OSPF networks must be configured in area 1

Answer: B C E

For more explanation click OSPF
 
 
 
 
 


 
 
 
 
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