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

What is a function of OSPF hello packets?

to send specifically requested link-state records
to discover neighbors and build adjacencies between them
to ensure database synchronization between routers
to request specific link-state records from neighbor routers

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

hello
DBD
LSR
LSU
LSAck

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

It is a link-state database that represents the network topology.
Its contents are the result of running the SPF algorithm.
When converged, all routers in an area have identical topology tables.
The topology table contains feasible successor routes.
The table can be viewed via the show ip ospf database command.
After convergence, the table only contains the lowest cost route entries for all known networks.

What does an OSPF area contain?

routers that share the same router ID
routers whose SPF trees are identical
routers that have the same link-state information in their LSDBs
routers that share the same process ID

What is used to facilitate hierarchical routing in OSPF?

the use of multiple areas
frequent SPF calculations
autosummarization
the election of designated routers

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

forwarding database
link-state database
adjacency database
routing table

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

builds the topology table
exchanges link-state advertisements
chooses the best path
executes the SPF algorithm

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 not change from the default value.
The dead interval will now be 30 seconds.
The dead interval will now be 60 seconds.
The dead interval will now be 15 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?

R1 automatically adjusts its own timers to match the R2 timers.
The R1 dead timer expires between hello packets from R2.
The hello timer on R2 expires every ten seconds.
The neighbor adjacency has formed.

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
router priority
list of neighbors
router ID
hello interval

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

0
1
10
255

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
link-state update
link-state request
link-state acknowledgment

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

when the two adjacent neighbors are interconnected over a point-to-point link
when all the routers in an OSPF area cannot form adjacencies
when the routers are interconnected over a common Ethernet network
when the two adjacent neighbors are in two different networks

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 5 minutes
every 10 minutes
every 30 minutes
every 60 minutes

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

a loopback interface that is configured with the highest IP address on the router
any IP address that is configured using the router-id command
the highest active interface IP that is configured on the router
the highest active interface that participates in the routing process because of a specifically configured network statement

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
to enable the SPF algorithm to determine the lowest cost path to remote networks
to facilitate the establishment of network convergence
to facilitate the transition of the OSPF neighbor state to Full

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

10.0.0.1
10.1.0.1
192.168.1.100
209.165.201.1

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

What does the number 11 represent?

the OSPF process ID on R1
the cost of the link to R1
the autonomous system number to which R1 belongs
the administrative distance that is manually assigned to R1
the area number where R1 is located

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 0.0.255.255 area 0
router(config-router)# network 172.16.0.0 0.0.15.255 area 0
router(config-router)# network 172.16.1.0 255.255.255.0 area 0
router(config-router)# network 172.16.1.0 0.0.0.0 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 FastEthernet 0/0 priority is 128.
The R4 router ID is 172.16.1.1.
R1 will be elected BDR.
The router ID on R2 is the loopback interface.
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.
Router R2 will become the DR and router R3 will become the BDR.
Router R1 will become the DR and router R2 will become the BDR.
Router R4 will become the DR and router R3 will become the BDR.

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

100000000
10000
1
100

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

782
74
128
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
ISP, R0-A, R0-B, and R0-C
ISP
R0-B and R0-C
ISP and R0-A
R0-A, R0-B, and R0-C

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

ping
show ip ospf neighbor
show ip interface brief
show ip protocols

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

R1# show ip ospf interface serial0/0/1
R1# show ip route ospf
R1# show ip ospf
R1# show ip ospf neighbor

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 interface brief
show ip ospf interface
show ip protocols
show ip route ospf

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.
Interface Fa0/0 is configured as a passive-interface on router R2.
Interface S0/0 is configured as a passive-interface on router R2.
Interface s0/0 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.
Use the highest active interface IP address that is configured on the router.
Use a loopback interface configured with the highest IP address on the router.
Use the highest IP address assigned to an active interface participating in the routing process.

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

load balancing equal-cost paths
declaring a neighbor to be inaccessible
choosing the best route
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
0.0.7.255
0.0.15.255
0.0.31.255

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

a unique router host name that is configured on the router
a unique phrase with no more than 16 characters
a 32-bit number formatted like an IPv4 address
an 8-bit number with a decimal value between 0 and 255
a character string with no space

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

HQ# copy running-config startup-config
HQ# resume
HQ# clear ip route *
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 allows all 192.168.1.0 networks to be advertised.
It tells the router which interface to turn on for the OSPF routing process.
It changes the router ID of the router to 192.168.1.1.
It enables OSPF on all interfaces on the router.

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

to force that specific link to be used in the destination route
to more accurately reflect the cost of links greater than 100 Mb/s
to enable the link for OSPF routing
to increase the speed of the link

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

Issue the clear ip ospf process command.
Change the subnet mask of interface FastEthernet 0/0 to 255.255.255.0.
Remove the passive interface command from interface FastEthernet 0/0.
Add the network 10.0.1.0 0.0.0.255 area 0 command to the OSPF process.

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

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.
Routers in all areas share the same link-state database and have a complete picture of the entire network.
A backbone area is not required.
Automatic route summarization occurs by default between areas.

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

if the router no longer receives hello packets
if the router receives an update with a hop count of 16
if the router receives an LSP with previously learned information
if the router no longer receives routing updates

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

Exchange
Init
ExStart
Two-way
Loading
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 priority of router C is changed to 255, then it will become the DR.
Router A will become the DR and router D will become the BDR.​
If the DR fails, the new DR will be router B.
If a new router with a higher priority is added to this network, it will become the DR.

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?

0.0.31.255
0.0.0.63
0.0.63.255
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 ipv6 ospf interface serial 0/0/0
show ip ospf neighbor
show ip ospf interface fastethernet 0/1
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?

0.0.63.255
0.0.0.63
0.0.0.3
0.0.0.7

Match each OSPF packet type to how it is used by a router. (Not all options are used.)

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?

.0.63.255
0.0.15.255
0.0.1.255
0.0.31.255

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?

0.0.63.255
0.0.3.255
0.0.31.255
0.0.0.255

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
0.0.0.7
0.0.0.3
0.0.63.255

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

building the topology table
selecting the router ID
exchanging link-state advertisements
injecting the default route

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

electing the designated router
establishing neighbor adjacencies
injecting the default route
exchanging link-state advertisements

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?

0.0.0.31
0.0.0.255
0.0.0.63
0.0.0.127

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

declaring a neighbor to be inaccessible
executing the SPF algorithm
load balancing equal-cost paths
choosing the best route

What type of address is 64.101.198.197?

public
private

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 0.0.255.255 area 0
router(config-router)# network 172.16.0.0 0.0.15.255 area 0
router(config-router)# network 172.16.1.0 0.0.0.255 area 0
router(config-router)# network 172.16.1.0 0.0.0.0 area 0

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

selecting the router ID
declaring a neighbor to be inaccessible
executing the SPF algorithm
building the topology table