CCNA 3 v7 Modules 1 – 2: OSPF Concepts and Configuration

What is a function of OSPF hello packets?

to discover neighbors and build adjacencies between them

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

LSU

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

* It is a link-state database that represents the network topology

* When converged, all routers in an area have identical topology tables

* 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.)

dead interval, 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.)

* to uniquely identify the router within the OSPF domain

* 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: R1(config)# router ospf 11 R1(config-router)# network 10.10.10.0 0.0.0.255 area 0

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.)

* R3 will be elected BDR.

* The R4 router ID is 172.16.1.1.

* 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.

Which task has to be performed on Router 1 for it to establish an OSPF adjacency with Router 2?

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

This is the algorithm used by OSPF.

Shortest Path First

This is where the details of the neighboring routers can be found.

Adjacency database

All the routers are in the backbone area.

Single-area OSPF

This is where you can find the topology table.

Link-state database

What is a benefit of multiarea OSPF routing?

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

second state

Init state

seventh state

Full state

fifth state

Exchange state

first state

Down state

fourth state

Exstart state

third state

Two-way state

sixth state

Loading state

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.)

* Init

* Two-way

* 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

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 128.107.0.0 255.255.255.192. What wildcard mask would the administrator use in the OSPF network statement?

0.0.0.63

link-state request packet

query another router for additional information

hello packet

establish and maintain adjacencies

database description packet

compare local topology to that sent by another router

link-state update packet

advertise new information

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 192.168.181.0 255.255.254.0. What wildcard mask would the administrator use in the OSPF network statement?

0.0.1.255

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 198.19.0.0 255.255.252.0. What wildcard mask would the administrator use in the OSPF network statement?

0.0.3.255

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 128.107.0.0 255.255.252.0. What wildcard mask would the administrator use in the OSPF network statement?

0.0.3.255

Which step in the link-state routing process is described by a router flooding link-state and cost information about each directly connected link?

exchanging link-state advertisements

Which step in the link-state routing process is described by a router sending Hello packets out all of the OSPF-enabled interfaces?

establishing neighbor adjacencies

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 64.100.0.0 255.255.255.0. What wildcard mask would the administrator use in the OSPF network statement?

0.0.0.255

Which step in the link-state routing process is described by a router inserting best paths into the routing table?

choosing the best route

What type of address is 64.101.198.197?

public

An OSPF router has three directly connected networks; 172.16.0.0/24, 172.16.1.0/24, and 172.16.2.0/24. Which OSPF network command would advertise only the 172.16.1.0 network to neighbors?

router(config-router)# network 172.16.1.0 0.0.0.255 area 0

Which step in the link-state routing process is described by a router building a link-state database based on received LSAs?

building the topology table