Alcatel-lucent Scalable IP Networks OSPF
OSPF assessment quiz in preparation for the NRS I Alcatel Exam.
- 1.
OSPF Discovers neighbors_______.
- A.
Only by manually configuring the router
- B.
By flooding updates
- C.
Using Hello advertisements
- D.
Using a host table
Correct Answer
C. Using Hello advertisementsExplanation
OSPF sends Hello packets to the 224.0.0.5 multicast IP address to discover other OSPF routers.Rate this question:
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- 2.
Which of the following is ​not a feature of the OSPF protocol?
- A.
It supports authentication.
- B.
It provides a loop-free topology.
- C.
It uses the Shortest Path First algorithm.
- D.
It uses a hop count-based metric.
Correct Answer
D. It uses a hop count-based metric.Explanation
OSPF uses a cost value on each interface that is based on the bandwidth of the link; it does not use a hop count.Rate this question:
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- 3.
Which logical interface is recommended for defining a router ID?
- A.
Ethernet interface
- B.
Chassis interface
- C.
MAC address
- D.
System interface
Correct Answer
D. System interfaceExplanation
It is recommended that you use the system interface as the router ID.Rate this question:
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- 4.
What is the primary purpose of the OSPF router ID?
- A.
To elect a designated router
- B.
To uniquely identify an OSPF router
- C.
To trace sequence numbers
- D.
To support LSA flooding
Correct Answer
B. To uniquely identify an OSPF routerExplanation
Every OSPF router must have a router ID to uniquely identify it for purposes of building the SPF tree and identifying its LSA updates.Rate this question:
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- 5.
LSA updates are sent in response to network changes and _____.
- A.
Every 30 minutes
- B.
After the Hello timer expires
- C.
When the DR detects the BDR has failed
- D.
Every 30 minutes provided new information needs to be transmitted
Correct Answer
A. Every 30 minutesExplanation
LSA updates are sent every 30 minutes in order to refresh the LSA. They are sent regardless of whether changes have occurred.Rate this question:
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- 6.
What does it mean to say that two OSPF routers are adjacent?
- A.
The routers are physically connected on a point-to-point link.
- B.
The routers are on a common network segment and have exchanged database information.
- C.
The routers have exchanged Hello packets.
- D.
The routers are in a single area.
Correct Answer
B. The routers are on a common network segment and have exchanged database information.Explanation
Routers that have shared database information are referred to as adjacent. Not all neighbor OSPF routers become adjacent.Rate this question:
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- 7.
What is required for OSPF routers on a point-to-point network to form an adjacency?
- A.
The DR must form an adjacency first.
- B.
The neighbor IP address must be configured.
- C.
They will automatically become adjacent provided certain OSPF configuration values match.
- D.
Nothing. OSPF routers on point-to-point links will always become adjacent.
Correct Answer
C. They will automatically become adjacent provided certain OSPF configuration values match.Explanation
The area ID and Hello and dead timers must match in the Hello packets.Rate this question:
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- 8.
Which of the following hello packet values is ​not involved in the adjacency process on point-to-point links?
- A.
The area ID
- B.
The priority
- C.
The Hello timer
- D.
The dead timer
Correct Answer
B. The priorityExplanation
The priority value is only applicable on OSPF broadcast networks.Rate this question:
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- 9.
In addition to having correct OSPF settings in the Hello packets, another value that can prevent routers from forming an adjacency in the event of a mismatch is _____.
- A.
The AS number
- B.
The OSPF MTU
- C.
The OSPF metric
- D.
The MPLS TE
Correct Answer
B. The OSPF MTUExplanation
This is based on the interface MTU and must match on each router.Rate this question:
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- 10.
The command to display the Link State Updates that a router has received is _____.
- A.
Show router ospf status
- B.
Show router ospf links
- C.
Showrouter ospf summary
- D.
Show router ospf database
Correct Answer
D. Show router ospf databaseExplanation
This command displays the LSAs that have been received from other OSPF routers.Rate this question:
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- 11.
There are many different types of LSAs in OSPF. The most common LSA type in point-to-point networks is _____.
- A.
The area LSA
- B.
The router LSA
- C.
The network LSA
- D.
The summary LSA
Correct Answer
B. The router LSAExplanation
The router LSA carries the local topology information for each router in the network.Rate this question:
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- 12.
If an OSPF router receives an LSA with a sequence number that is ​equal to the sequence number it already has for that LSA, it will _____.
- A.
Silently drop the LSA
- B.
Send a rejection notice to the sending router
- C.
Drop the LSA and send an acknowledgement
- D.
Drop the LSA and forward it to its adjacent routers
Correct Answer
C. Drop the LSA and send an acknowledgementExplanation
The router already has the information so it will drop the LSA, but all LSAs must be acknowledged.Rate this question:
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- 13.
Which of the following is false regarding the Shortest Path First algorithm that OSPF uses?
- A.
It determines the optimal route to each network.
- B.
It creates a loop-free path to each network.
- C.
It is run only on the router that originates an LSA update.
- D.
It runs every time a new LSA is received.
Correct Answer
C. It is run only on the router that originates an LSA update.Explanation
Whenever an LSA update is flooded throughout the network, all routers must rerun the SPF algorithm.Rate this question:
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- 14.
Which of the following correctly identifies the order of steps for two OSPF routers to become fully adjacent?
- A.
Exchange, Loading, SPF, Adjacent
- B.
Exchange, ExStart, Loading
- C.
ExStart, Exchange, Loading, Full
- D.
ExStart, Exchange, Loading, Adjacent
Correct Answer
C. ExStart, Exchange, Loading, FullExplanation
This is the correct order.Rate this question:
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- 15.
Which of the following default metrics is not correct for the given interface speed?
- A.
1-Gbps link = 100
- B.
16-Mbps link = 6,250
- C.
1.544-Mbps link = 64,766
- D.
622-Mbps link = 16
Correct Answer
D. 622-Mbps link = 16Explanation
(100 Gbps)/(622 Mbps) = 160, not 16.Rate this question:
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- 16.
What is the cost value of an OSPF interface on the Alcatel-Lucent 7750 SR?
- A.
It is based on the configuration of the global OSPF cost variable, which has a default value of 10.
- B.
It is based on the configuration of the global OSPF cost variable, which has a default value of 100.
- C.
It is based on a reference bandwidth, which has a default value of 10 Gbps.
- D.
It is based on a reference bandwidth, which has a default value of 100 Gbps.
Correct Answer
D. It is based on a reference bandwidth, which has a default value of 100 Gbps.Explanation
The cost value in OSPF is dependent on the default OSPF reference bandwidth, which is 100Gbs.Rate this question:
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- 17.
A router has an OSPF broadcast interface declared as passive. How will this be represented in the Router LSA originated by the router?
- A.
The Router LSA will contain a stub network link type to describe the interface.
- B.
The Router LSA will contain a transit link type to describe the interface.
- C.
The Router LSA will contain a point-to-point link type to describe the interface.
- D.
The Router LSA will contain a point-to-point link type and a stub network link type to describe the interface.
- E.
The Router LSA will not describe the interface.
Correct Answer
A. The Router LSA will contain a stub network link type to describe the interface.Explanation
All passive interfaces, loopback interfaces, system interfaces, and interfaces that have not yet formed an adjacency are represented in the Router LSA as stub networks.Rate this question:
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- 18.
Which statement is not correct regarding an OSPF Type 1 LSA?
- A.
An OSPF Type 1 LSA is originated by every OSPF router.
- B.
An OSPF Type 1 LSA is called a Router LSA.
- C.
The OSPF Type 1 LSA is flooded throughout the autonomous system.
- D.
The OSPF Type 1 LSA describes the router’s directly connected links.
- E.
The OSPF Type 1 LSA contains an age field.
Correct Answer
C. The OSPF Type 1 LSA is flooded throughout the autonomous system.Explanation
The OSPF Router LSA (Type 1 LSA) is not flooded throughout the autonomous system; it is only flooded within the area in which it was originated.Rate this question:
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- 19.
A 7750 SR has an OSPF adjacency with its neighbor using a router ID derived from the last four octets of the chassis MAC address. The system ​interface IP address, router ID, and OSPF router ID are then configured. Assuming these are the only commands executed, what router ID will be seen by the OSPF neighbor?
- A.
The router ID seen by the neighbor will be derived from the last four octets of the chassis MAC address.
- B.
The router ID seen by the neighbor will be derived from the system interface address.
- C.
The router ID seen by the neighbor will be derived from the configured router ID.
- D.
The router ID seen by the neighbor will be derived from the configured OSPF router ID.
Correct Answer
A. The router ID seen by the neighbor will be derived from the last four octets of the chassis MAC address.Explanation
The router ID value does not change until the OSPF process is restarted. If OSPF is shut down and restarted, the router ID will be configured with the OSPF router ID value.Rate this question:
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- 20.
Which of the following is not a field in an OSPF Hello packet that must match for a successful state transition to the 2-Way state?
- A.
Dead Interval
- B.
Authentication Type
- C.
MTU
- D.
Area ID
- E.
Stub Flag
Correct Answer
C. MTUExplanation
The MTU must match, but the MTU value is not in the Hello packet; it is in the Database Description packet. If there is an MTU mismatch on the link, the routers will move past the OSPF 2-Way state. The other four parameters are all contained in the Hello packet and must match for the adjacency to continue.Rate this question:
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- 21.
When does an OSPF router transition to the 2-Way state?
- A.
After a Link State Request is received from a neighbor
- B.
After the first Link State Update is received from a neighbor
- C.
After a Hello packet that contains its own router ID is received from a neighbor
- D.
After the first Link State Acknowledgment is received from a neighbor
- E.
After a Database Description packet is received from a neighbor
Correct Answer
C. After a Hello packet that contains its own router ID is received from a neighborExplanation
An OSPF router transitions to the 2-Way state after a Hello packet that contains its own router ID is received from a neighbor.Rate this question:
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- 22.
Two routers R1 and R2 have a point-to-point OSPF adjacency. R1 has a priority of 15 and an OSPF router ID of 10.10.10.10. R2 has a priority of 25 and an OSPF router ID of 5.5.5.5. Which router will be the Designated Router?
- A.
R1 will be the Designated Router.
- B.
R2 will be the Designated Router.
- C.
The first router to initialize will be the Designated Router.
- D.
There will be no Designated Router.
Correct Answer
D. There will be no Designated Router.Explanation
OSPF routers on a point-to-point link do not elect a designated router, only routers on a broadcast link.Rate this question:
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- 23.
When two routers are in the OSPF ExStart state, how is the initial Database Description sequence number determined?
- A.
Both routers send a DBD packet with an initial sequence number, and the highest is used.
- B.
The sequence number of the router with the highest priority is used.
- C.
The sequence number of the router that sends the first Database Description packet is used.
- D.
The sequence number of the router with the highest router ID is used.
Correct Answer
D. The sequence number of the router with the highest router ID is used.Explanation
Both OSPF routers send an initial Database Description packet. The router with the highest router ID becomes the master, and the sequence number in its Database Description packet is used.Rate this question:
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- 24.
R1 and R2 are directly connected to each other and running OSPF on the link. The OSPF interface MTU of both routers is different, but the port MTU of each router is the same. What state will the adjacency be in?
- A.
The adjacency will be in the Init state.
- B.
The adjacency will be in the 2-Way state.
- C.
The adjacency will be in the ExStart state.
- D.
The adjacency will be in the Full state.
Correct Answer
C. The adjacency will be in the ExStart state.Explanation
By default, the OSPF MTU is derived from the port MTU. However, in this case, the OSPF MTU is explicitly set on the OSPF interface; thus there is definitely an MTU mismatch. Because the MTU is carried in the Database Description packet and the values do not match, the routers will stay in the ExStart state.Rate this question:
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- 25.
What is the main purpose of the DBD packet?
- A.
The DBD packet is used to carry LSAs between routers.
- B.
The DBD packet is used in the OSPF neighbor discovery mechanism.
- C.
The DBD packet is used to provide summary LSA information to each router so that specific LSAs can be requested.
- D.
The DBD packet is used to withdraw LSA information when there is a topology change.
Correct Answer
C. The DBD packet is used to provide summary LSA information to each router so that specific LSAs can be requested.Explanation
The DBD packet is used to provide summary LSA information to each router so that specific LSAs can be requested.Rate this question:
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- 26.
Which statement is correct regarding OSPF LSA exchange between routers?
- A.
A router requests one LSA at a time using an LSR.
- B.
A router can request multiple LSAs using a single LS The size of the LSR is dependent on the MTU settings.
- C.
A router can request multiple LSAs using a single LS The size of the LSR is dependent on the value of the maximum LSA size parameter.
- D.
A router never requests LSAs; they are always flooded.
Correct Answer
B. A router can request multiple LSAs using a single LS The size of the LSR is dependent on the MTU settings.Explanation
A router can request multiple LSAs using a single LSR. The size of the LSR is limited by the OSPF interface MTU setting.Rate this question:
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- 27.
Which statement best describes what happens when an OSPF receives an LSA with a higher sequence number than the LSA in its database?
- A.
The router acknowledges the LSA but does not add it to its link-state database and does not flood it to its neighbors.
- B.
The router does not acknowledge the LSA but sends a copy of the LSA from its database to the neighbor from which it received the LSA.
- C.
The router acknowledges the LSA and floods it to its neighbors but does not add it to its link-state database.
- D.
The router acknowledges the LSA, adds it to its own database, and floods it to its neighbors.
Correct Answer
D. The router acknowledges the LSA, adds it to its own database, and floods it to its neighbors.Explanation
A higher sequence number indicates that the received LSA has newer information than what the router currently has in its database. Therefore, the router will acknowledge the LSA, flood it to its neighbors, and add the LSA to its own database. Answer A describes the action when the sequence number is the same and B describes the action when the sequence number is lower (the LSA is out of date).Rate this question:
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- 28.
A router has four interfaces that are added to OSPF. Two point-to-point interfaces are in Area 1. There is one point-to-point interface in Area 2 and one broadcast interface in Area 3. How many Network LSAs will be originated by the router?
- A.
The router will not originate any Network LSAs.
- B.
The router will originate one Network LSAs.
- C.
The router will originate two Network LSAs.
- D.
The router will originate four Network LSAs.
- E.
It is not possible to determine with the given information.
Correct Answer
A. The router will not originate any Network LSAs.Explanation
Network LSAs are originated by the elected DR for an OSPF broadcast network, and we do not know if the router is the DR or not. If the router is the DR for the broadcast network in area 3, the router originates one Network LSA. If the router is not the DR for the broadcast network in area 3, it does not originate any Network LSAs. Network LSAs are not originated for any of the point-to-point networks.Rate this question:
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- 29.
Which of the following best describes the election of the DR on a broadcast interface in OSPF when all routers have the same priority value?
- A.
The router with the lowest router ID is always the DR.
- B.
The router with the highest router ID is always the DR.
- C.
The router with the highest IP address on the broadcast interface is always the DR.
- D.
The router with the lowest IP address on the broadcast interface is always the DR.
- E.
The router that has been up the longest is usually the DR, since DR election is non-preemptive.
Correct Answer
E. The router that has been up the longest is usually the DR, since DR election is non-preemptive.Explanation
If the priority of the routers is the same and there is no DR already elected, the router with the highest router ID on the network is elected DR. However, DR election is non-preemptive. If a router is already DR, it remains DR even when a router with a higher priority joins the network. Thus, the DR is often the router on the network that has been up the longest.Rate this question:
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- 30.
A router has been elected the DR on a broadcast OSPF interface on a subnet with three other routers. How will the link-state topology be described by routers on the subnet? Choose the best statement.
- A.
The DR originates a Router LSA that includes the broadcast interface. The other routers on the subnet do not originate any LSAs that include the broadcast interface.
- B.
The DR originates only a Network LSA that describes the broadcast network.
- C.
The DR originates a Router LSA that includes the broadcast interface and a Network LSA that includes the broadcast interface. The other routers on the subnet do not originate any LSAs that include the broadcast interface.
- D.
All routers on the subnet originate a Router LSA that includes the broadcast interface and a Network LSA that describes the broadcast network.
- E.
All routers on the subnet originate a Router LSA that includes the broadcast interface. Only the DR originates a Network LSA that describes the broadcast network.
Correct Answer
E. All routers on the subnet originate a Router LSA that includes the broadcast interface. Only the DR originates a Network LSA that describes the broadcast network.Explanation
Every OSPF router originates a Router LSA that describes all their interfaces regardless of the interface types. Therefore, answers A, B, and C are incorrect. Only the DR and BDR for a broadcast interface originate the Network LSA and, therefore, D is incorrect.Rate this question:
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Mar 21, 2023Quiz Edited by
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Jun 28, 2017Quiz Created by
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