CCNA 3 v7 Modules 1 – 2: OSPF Concepts and Configuration Exam Answers (w/Module 1 and 2 from check your understanding in netacad)

What is a function of OSPF hello packets?

to discover neighbors and build adjacencies between them

Which OPSF packet contains the different types of link-state advertisements?

LSU

Which statements describe features of the OSPF topology table? (Choose three.)

1.) The table can be viewed via the show ip ospf database command.

2.) It is a link-state database that represents the network topology.

3.) When converged, all routers in an area have identical topology tables.

What does an OSPF area contain?

routers that have the same link-state information in their LSDBs

A router is participating in an OSPFv2 domain. What will always happen if the dead interval expires before the router receives a hello packet from an adjacent DROTHER OSPF router?

OSPF will remove that neighbor from the router link-state database.

What is the order of packet types used by an OSPF router to establish convergence?

Hello, DBD, LSR, LSU, LSAck

What is a feature of the OSPF routing protocol?​

It scales well in both small and large networks.

What is used to create the OSPF neighbor table?

adjacency database

What is identical on all OSPF routers within a single area?

link-state database

What function is performed by the OSPF designated router?

dissemination of LSAs

What are two reasons for creating an OSPF network with multiple areas? (Choose two.)

1.) to reduce use of memory and processor resources

2.) to reduce SPF calculations

At which OSPF state are neighbor routers converged and able to exchange routing updates?

Full

The OSPF hello timer has been set to 15 seconds on a router in a point-to-point network. By default, what is the dead interval on this router?

60 seconds

What happens immediately after two OSPF routers have exchanged hello packets and have formed a neighbor adjacency?

They exchange abbreviated lists of their LSDBs.

Which statement is correct about multiarea OSPF?

Arranging routers into areas partitions a large autonomous system in order to lighten the load on routers.

Which OSPF data structure is identical in all routers in an OSPF area after convergence?

Link-state database

What are the purposes of an OSPF router ID? (Choose two.)

1.) To facilitate router participation in the election of the designated router

2.) To uniquely identify the router within the OSPF domain

Which statement describes a multiarea OSPF network?

It has a core backbone area with other areas connected to the backbone area.

What are the advantages of using multiarea OSPF? (Choose two.)

1.) It improves routing efficiency by reducing the routing table and linkstate update overhead.

2.) Topology changes in one area do not cause SPF recalculations in other areas.

Which command can be used to verify the contents of the LSDB in an OSPF area?

show ip ospf database

Which of the following facilitates hierarchical routing in OSPF?

The use of multiple areas

Which step does an OSPF-enabled router take immediately after the OSPF router builds the topology table?

Executes the SPF algorithm

Which type of OSPFv2 packet contains an abbreviated list of the LSDB of a sending router and is used by receiving routers to check against the local LSDB?

Database Description

Which OSPF states are performed prior to two routers forming a neighbor adjacency? (Choose three.)

1.) Down

2.) Init

3.) Two-Way

In an OSPF network, when are DR and BDR elections required?

When the routers are interconnected over a common Ethernet network

When an OSPF network is converged and no network topology change has been detected by a router, how often are LSU packets sent to neighboring routers?

Every 30 minutes

Which criterion is preferred by the router to choose a router ID?

the router-id rid command

Which wildcard mask would be used to advertise the 192.168.5.96/27 network as part of an OSPF configuration?

0.0.0.31

The following three networks are directly connected to an OSPF router; 192.168.0.0/24, 192.168.1.0/24, and 192.168.2.0/24. Which OSPF network command would advertise only the 192.168.1.0 network to neighbors?

router(config-router)# network 192.168.1.0 0.0.0.255 area 0

Which three parameters should match in order for a pair of routers to form an adjacency when running OSPFv2? (Choose three.)

1.) OSPFv2 type of network

2.) hello timer

3.) subnet mask

What are two features of the OSPF routing protocol? (Choose two.)

1.) uses Dijkstra's algorithm to build the SPF tree

2.) calculates its metric using bandwidth

A router with two LAN interfaces, two WAN interfaces, and one configured loopback interface is operating with OSPF as its routing protocol. What does the router OSPF process use to assign the router ID?

the loopback interface IP address

Which verification command would identify the specific interfaces on a router that were configured with the passive-interface command?

show ip protocols

Which command, if applied on an OSPF router, would give a Gigabit Ethernet interface a lower cost than a Fast Ethernet interface?

(config-router)# auto-cost reference-bandwidth 1000

A network administrator has just changed the router ID on a router that is working in an OSPFv2 environment. What should the administrator do to reset the adjacencies and use the new router ID?

Issue the clear ip ospf process privileged mode command.

Which command can be used to view the OSPF hello and dead time intervals?

show ip ospf interface

What does the SPF algorithm consider to be the best path to a network?

The path that includes the fastest cumulative bandwidth links.

What is one use of the router ID in OSPF routing?

The router ID can be used to break a tie in the election process.

What is the first criterion used by OSPF routers to elect a DR?

highest priority

Which command could be used on a router to ensure that an OSPF adjacency is formed with another router?

show ip ospf neighbor

A router in an OSPF enterprise network has a default static route that has been configured via the interface that connects to the ISP. Which command would the network administrator apply on this router so that other routers in the OSPF network will use this default route?

default-information originate

A router is participating in an OSPFv2 domain. What will always happen if the Dead interval expires before the router receives a Hello packet from an adjacent OSPF router?

OSPF will remove that neighbor from the router's link-state database.

Which command would be used to determine if an OSPF routing protocol- initiated relationship had been made with an adjacent router?

show ip ospf neighbor

Which command is used to verify the OSPFv2 router ID, the interfaces explicitly configured to advertise OSPF routes, the passive interfaces, the neighbors the router is receiving updates from, and the default administrative distance, which is 110 for OSPF?

show ip protocols

Two OSPFv2 routers are interconnected using a point-to-point WAN link.Which command could be used to verify the configured Hello and Dead timer intervals?

show ip ospf interface serial 0/0/0

You are troubleshooting convergence and adjacency issues in an OSPFv2 network and have noticed that network route entries are missing from the routing table. Which commands provide additional information about the state of router adjacencies, timer intervals, and the area ID? (Choose two.)

1.) show ip ospf interface

2).) show ip ospf neighbor

A network engineer has manually configured the Hello interval to 15 seconds on an interface of a router that is running OSPFv2. By default, how will the Dead interval on the interface be affected?

The Dead interval will now be 60 seconds.

To establish a neighbor adjacency, two OSPF routers exchange Hello packets. Which values in the Hello packets must match on the two routers? (Choose two.)

1.) Dead interval

2.) Hello interval

What is the default router priority value for all Cisco OSPF routers?

1

What indicates to a link-state router that a neighbor is unreachable?

The router no longer receives Hello packets.

Which of the following will OSPF use when it chooses its router ID?

A loopback interface that is configured with the highest IP address on the router

An OSPF router has three directly connected networks; 10.1.0.0/16, 10.1.1.0/16, and 10.1.2.0/16. Which OSPF network command would advertise only the 10.1.1.0 network to neighbors?

router(config-router)# network 10.1.1.0 0.0.0.255 area 0

By default, what is the OSPF cost for a link with Gigabit Ethernet interfaces?

1

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 64.100.1.64 255.255.255.192. Which OSPF network statement should be configured?

network 64.100.1.64 0.0.0.63 area 0

Which of these factors will prevent two routers from forming an OSPFv2 adjacency? (Choose two.)

1.) Mismatched OSPF Hello or Dead timers

2.) Mismatched subnet masks on the link interfaces

From this point on lahat manggagaling na sa Module 1-2 na quiz na pinagsama kaya may mga mauulit na tanong, yung mga kanina galing module1 at module 2 na check your understanding sa netacad

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What is a function of OSPF hello packets?

to discover neighbors and build adjacencies between them

Which OPSF packet contains the different types of link-state advertisements?

LSU

Which three statements describe features of the OSPF topology table? (Choose three.)

1.) It is a link-state database that represents the network topology.

2.) When converged, all routers in an area have identical topology tables.

3.) The table can be viewed via the show ip ospf database command.

What does an OSPF area contain?

routers that have the same link-state information in their LSDBs

What is used to facilitate hierarchical routing in OSPF?

the use of multiple areas

Which OSPF data structure is identical on all OSPF routers that share the same area?

link-state database

Which step does an OSPF-enabled router take immediately after establishing an adjacency with another router?

exchanges link-state advertisements

A network engineer has manually configured the hello interval to 15 seconds on an interface of a router that is running OSPFv2. By default, how will the dead interval on the interface be affected?

The dead interval will now be 60 seconds.

Refer to the exhibit. A network administrator has configured the OSPF timers to the values that are shown in the graphic. What is the result of having those manually configured timers?

The R1 dead timer expires between hello packets from R2.

To establish a neighbor adjacency two OSPF routers will exchange hello packets. Which two values in the hello packets must match on both routers? (Choose two.)

1.) dead interval

2.) hello interval

What is the default router priority value for all Cisco OSPF routers?

1

Which type of OSPFv2 packet contains an abbreviated list of the LSDB of a sending router and is used by receiving routers to check against the local LSDB?

database description

In an OSPF network when are DR and BDR elections required?

when the routers are interconnected over a common Ethernet network

When an OSPF network is converged and no network topology change has been detected by a router, how often will LSU packets be sent to neighboring routers?

every 30 minutes

What will an OSPF router prefer to use first as a router ID?

any IP address that is configured using the router-id command

What are the two purposes of an OSPF router ID? (Choose two.)

1.) to uniquely identify the router within the OSPF domain

2.) to facilitate router participation in the election of the designated router

Refer to the exhibit. If no router ID was manually configured, what would router Branch1 use as its OSPF router ID?

192.168.1.100

A network technician issues the following commands when configuring a router:

What does the number 11 represent?

the OSPF process ID on R1

An OSPF router has three directly connected networks; 172.16.0.0/16, 172.16.1.0/16, and 172.16.2.0/16. Which OSPF network command would advertise only the 172.16.1.0 network to neighbors?

router(config-router)# network 172.16.1.0 255.255.255.0 area 0

Refer to the exhibit. Which three statements describe the results of the OSPF election process of the topology that is shown in the exhibit? (Choose three.)

1.) R3 will be elected BDR.

2.) The R4 router ID is 172.16.1.1.

3.) R2 will be elected DR.

Refer to the exhibit. If the switch reboots and all routers have to re-establish OSPF adjacencies, which routers will become the new DR and BDR? 

Router R4 will become the DR and router R1 will become the BDR.

By default, what is the OSPF cost for any link with a bandwidth of 100 Mb/s or greater?

1

Refer to the exhibit. What is the OSPF cost to reach the router A LAN 172.16.1.0/24 from B?

65

Refer to the exhibit. On which router or routers would a default route be statically configured in a corporate environment that uses single area OSPF as the routing protocol? 

R0-A

What command would be used to determine if a routing protocol-initiated relationship had been made with an adjacent router?

show ip ospf neighbor

Refer to the exhibit. Which command did an administrator issue to produce this output?

R1# show ip ospf interface serial0/0/1

Which command is used to verify that OSPF is enabled and also provides a list of the networks that are being advertised by the network?​

show ip protocols

Refer to the exhibit. A network administrator has configured OSPFv2 on the two Cisco routers but PC1 is unable to connect to PC2. What is the most likely problem?

Interface Fa0/0 has not been activated for OSPFv2 on router R2.

What is the recommended Cisco best practice for configuring an OSPF-enabled router so that each router can be easily identified when troubleshooting routing issues?

Configure a value using the router-id command.

Which step in the link-state routing process is described by a router running an algorithm to determine the best path to each destination?

executing the SPF algorithm

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 192.168.223.0 255.255.254.0. What wildcard mask would the administrator use in the OSPF network statement?

0.0.1.255

What is the format of the router ID on an OSPF-enabled router?

a 32-bit number formatted like an IPv4 address

After modifying the router ID on an OSPF router, what is the preferred method to make the new router ID effective?

HQ# clear ip ospf process

In an OSPFv2 configuration, what is the effect of entering the command network 192.168.1.1 0.0.0.0 area 0 ?

It tells the router which interface to turn on for the OSPF routing process.

What is the reason for a network engineer to alter the default reference bandwidth parameter when configuring OSPF?

to more accurately reflect the cost of links greater than 100 Mb/s

Open the PT Activity. Perform the tasks in the activity instructions and then answer the question.

Change the subnet mask of interface FastEthernet 0/0 to 255.255.255.0.

Match the description to the term. (Not all options are used.)

1.) This is the algorithm used by OSPF - Shortest Path First

2.) This is where the details of the neigbouring routers can be found - Adjacency Database

3.) This is where you can find the topology table - Link-state database

4.) all routers are in the backbone area - single-area ospf

What is a benefit of multiarea OSPF routing?

Topology changes in one area do not cause SPF recalculations in other areas.

Match the OSPF state with the order in which it occurs. (Not all options are used.)

ayan

What indicates to a link-state router that a neighbor is unreachable?

if the router no longer receives hello packets

Which three OSPF states are involved when two routers are forming an adjacency? (Choose three.)

1.) Init

2.) Two-Way

3.) Down

Refer to the exhibit. Suppose that routers B, C, and D have a default priority, and router A has a priority 0. Which conclusion can be drawn from the DR/BDR election process?​ 

If the DR fails, the new DR will be router B.

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 64.102.0.0 255.255.255.128. What wildcard mask would the administrator use in the OSPF network statement?

0.0.0.127

Which command will a network engineer issue to verify the configured hello and dead timer intervals on a point-to-point WAN link between two routers that are running OSPFv2?

show ip ospf interface serial 0/0/0