CCNA 3 Chapter 8: Single-Area OSPF (v5.0.3 + v6.0) Exam Answers

Q1. By default, what is the OSPF cost for any link with a bandwidth of 100 Mb/s or greater?

100
100000000
1
10000

Explanation: OSPF uses the formula: Cost = 100,000,000 / bandwidth. Because OSPF will only use integers as cost, any bandwidth of 100 Mb/s or greater will all equal a cost of 1.

Discussion

Q2. Which command will verify that a router that is running OSPFv3 has formed an adjacency with other routers in its OSPF area?

show ipv6 interface brief
show ipv6 ospf neighbor
show ipv6 route ospf
show running-configuration

Explanation: The show ipv6 ospf neighbor command will verify neighbor adjacencies for OSPFv3 routers. The other options do not provide neighbor information.

Discussion

Q3. Which OSPF component is identical in all routers in an OSPF area after convergence?

adjacency database
link-state database
SPF tree
routing table

Explanation: Each OSPF router views the network differently as the root of a unique SPF tree. Each router builds adjacencies based on its own position in the topology. Each routing table in the area is developed individually through the application of the SPF algorithm. The link-state database for an area, however, must reflect the same information for all routers.

Discussion

Q4. Which OPSF packet contains the different types of link-state advertisements?

DBD
LSR
hello
LSAck
LSU

Explanation: Link-state update (LSU) packets contain different types of link-state advertisements (LSAs). The LSUs are used to reply to link-state requests (LSRs) and to announce new information.

Discussion

Q5. Which three addresses could be used as the destination address for OSPFv3 messages? (Choose three.)

FF02::AFF02::1:2
2001:db8:cafe::1
FE80::1
FF02::6
FF02::5

Explanation: OSPFv6 messages can be sent to either the OSPF router multicast FF02::5, the OSPF DR/BDR multicast FF02::6, or the link-local address.

Discussion

Q6. Fill in the blank.

OSPF uses cost as a metric.

Explanation: The OSPF metric is cost. The lowest cost path to a remote destination is the preferred path and is installed in the routing table.

Discussion

Q7. What are the two purposes of an OSPF router ID? (Choose two.)

to enable the SPF algorithm to determine the lowest cost path to remote networks
to facilitate the establishment of network convergence
to uniquely identify the router within the OSPF domain
to facilitate router participation in the election of the designated router
to facilitate the transition of the OSPF neighbor state to Full

Explanation: OSPF router ID does not contribute to SPF algorithm calculations, nor does it facilitate the transition of the OSPF neighbor state to Full. Although the router ID is contained within OSPF messages when router adjacencies are being established, it has no bearing on the actual convergence process.

Discussion

Q8. A network administrator enters the command ipv6 router ospf 64 in global configuration mode. What is the result of this command?

The router will be assigned an autonomous system number of 64.
The router will be assigned a router ID of 64.
The reference bandwidth will be set to 64 Mb/s.
The OSPFv3 process will be assigned an ID of 64.

Explanation: The basic command to implement OSPFv3 on a router uses the same process-id parameter as OSPFv2 to assign a locally-significant number to the OSPF process. OSPF does not use autonomous system numbers. Following the assignment of the process ID, a prompt will direct the user to manually assign a router ID. After the router ID is assigned, the reference bandwidth can be set.

Discussion

Q9. What happens immediately after two OSPF routers have exchanged hello packets and have formed a neighbor adjacency?

They exchange DBD packets in order to advertise parameters such as hello and dead intervals.
They request more information about their databases.
They exchange abbreviated lists of their LSDBs.
They negotiate the election process if they are on a multiaccess network.

Explanation: During the exchange of hello packets, OSPF routers negotiate the election process and set the OSPF parameters. DBD packets are exchanged after that step has been completed. DBD packets contain abbreviated lists of link-state information. After that information has been exchanged, OSPF routers exchange Type 3 LSR packets to request further information.

Discussion

Q10. Open the PT Activity. Perform the tasks in the activity instructions and then complete the task. What message is displayed on www.ciscoville.com?

Completion!
Success!
Converged!
Finished!

Explanation:

The correct configuration on R1 is:
router ospf 10
network 192.168.2.0 0.0.0.255 area 0
network 10.0.10.0 0.0.0.3 area 0

The correct configuration on R2 is:
router ospf 10
network 10.0.10.0 0.0.0.3 area 0
network 10.0.10.4 0.0.0.3 area 0
network 172.16.5.0 0.0.0.255 area 0

Discussion

Q11. What are two reasons that will prevent two routers from forming an OSPFv2 adjacency? (Choose two.)

a mismatched Cisco IOS version that is used
one router connecting to a FastEthernet port on the switch and the other connecting to a GigabitEthernet port
use of private IP addresses on the link interfaces
mismatched OSPF Hello or Dead timers
mismatched subnet masks on the link interfaces

Explanation: There may be several reasons why two routers running OSPF will fail to form an OSPF adjacency, including these:
The subnet masks do not match, causing the routers to be on separate networks.
OSPF Hello or Dead Timers do not match.
OSPF network types do not match.
There is a missing or incorrect OSPF network command.
Mismatched IOS versions, the use of private IP addresses, and different types of interface ports used on a switch are not causes for an OSPF
adjacency failing to form between two routers.

Discussion

Q12. What does a Cisco router use automatically to create link-local addresses on serial interfaces when OSPFv3 is implemented?

the MAC address of the serial interface, the FE80::/10 prefix, and the EUI-64 process
an Ethernet interface MAC address available on the router, the FE80::/10 prefix, and the EUI-64 process
the FE80::/10 prefix and the EUI-48 process
the highest MAC address available on the router, the FE80::/10 prefix, and the EUI-48 process

Explanation: Since serial interfaces do not have MAC addresses, OSPFv3 automatically assigns a link-local address to them derived from the first available MAC address from the pool of Ethernet interface addresses on the router. A FE80::/10 prefix is added. The router then applies the EUI-64 process to the MAC address by inserting FFFE into the middle of the existing 48-bit address and flipping the seventh bit.

Discussion

Q13. Single area OSPFv3 has been enabled on a router via the ipv6 router ospf 20 command. Which command will enable this OSPFv3 process on an interface of that router?

ipv6 ospf 20 area 20
ipv6 ospf 0 area 0
ipv6 ospf 0 area 20
ipv6 ospf 20 area 0

Explanation: The command to enable an OSPFv3 process on a router interface is ipv6 ospf process-id area area-id. In the case the process ID is 20 and the area ID is 0.

Discussion

Q14. Fill in the blank.

The election of a DR and a BDR takes place on multiaccess networks, such as Ethernet networks.

Explanation: There is no need to have a DR/BDR election on a point-to-point link.

Discussion

Q15. Which command will provide information specific to OSPFv3 routes in the routing table?

show ip route ospf
show ipv6 route
show ipv6 route ospf
show ip route

Explanation: The show ipv6 route ospf command gives specific information that is related to OSPFv3 routes in the routing table. The show ipv6 route command will show the entire routing table. The show ip route and show ip route ospf commands are used with OSPFv2.

Discussion

Q16. Which command should be used to check the OSPF process ID, the router ID, networks the router is advertising, the neighbors the router is receiving updates from, and the default administrative distance?

show ip ospf neighbor
show ip ospf
show ip protocols
show ip ospf interface

Explanation: The show ip ospf neighbor command is used to verify that the router has formed an adjacency with its neighboring routers. The show ip ospf command displays the OSPF process ID and router ID, the OSPF area information, as well as the last time the SPF algorithm was calculated. The show ip ospf interface command provides detailed information about every OSPF-enabled interface.

Discussion

Q17. What is the metric that is used by OSPF?

cost
distance
hop count
delay

Explanation: OSPF uses cost as a metric. OSPF calculates cost inversely to the bandwidth of an interface. The higher the interface bandwidth, the lower the cost of the interface.

Discussion

Q18. What function is performed by the OSPF designated router?

summarizing routes between areas
dissemination of LSAs
maintaining the link-state database
redistribution of external routes into OSPF

Explanation: OSPF designated routers are elected on multiaccess networks to disseminate LSAs to other OSPF routers. By having a single router disseminate LSAs, the exchanging of LSAs is more efficient.

Discussion

Q19. What is used to create the OSPF neighbor table?

adjacency database
link-state database
forwarding database
routing table

Explanation: The adjacency database is used to create the OSPF neighbor table. The link-state database is used to create the topology table, and the forwarding database is used to create the routing table.

Discussion

Q20. When a network engineer is configuring OSPFv3 on a router, which command would the engineer issue immediately before configuring the router ID?

clear ipv6 ospf process
interface serial 0/0/1
ipv6 router ospf 10
ipv6 ospf 10 area 0

Explanation: The OSPFv3 router ID is configured in the IPv6 router configuration mode. The clear ipv6 ospf process privileged EXEC command forces OSPF on the router to renegotiate neighbor adjacencies. The interface serial 0/0/1 command causes the router to enter interface configuration mode where OSPFv3 is enabled by issuing the ipv6 ospf process-id area area-id command.

Discussion

Q21. What will an OSPF router prefer to use first as a router ID?

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

Explanation: The first preference for an OSPF router ID is an explicitly configured 32-bit address. This address is not included in the routing table and is not defined by the network command. If a router ID that is configured through the router-id command is not available, OSPF routers next use the highest IP address available on a loopback interface, as loopbacks used as router IDs are also not routable addresses. Lacking either of these alternatives, an OSPF router will use the highest IP address from its active physical interfaces.

Discussion

Q22. Question

Explanation: No answer description available for this question

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Q23. Question

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Q24. Question

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Q25. Question

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Q26. Question

Explanation: No answer description available for this question

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Q27. Question

Explanation: No answer description available for this question

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Q28. Question

Explanation: No answer description available for this question

Discussion

Q29. Which three statements are advantages of using automatic summarization? (Choose three.)

It maximizes the number of routes in the routing table.
It increases the size of routing updates.
It reduces the frequency of routing updates.
It ensures that traffic for multiple subnets uses one path through the internetwork.
It improves reachability in discontiguous networks.
It decreases the number of entries in the routing table.

Explanation: No answer description available for this question

Discussion

Q30. Question

Explanation: No answer description available for this question

Discussion

Q31. Which address best summarizes the IPv6 addresses 2001:DB8:ACAD::/48, 2001:DB8:9001::/48, and 2001:DB8:8752::/49?

2001:DB8:8000::/34
2001:DB8:8000::/36
2001:DB8:8000::/47
2001:DB8:8000::/48

Explanation: No answer description available for this question

Discussion

Q32. What is a characteristic of manual route summarization?

requires high bandwidth utilization for the routing updates
reduces total number of routes in routing tables
cannot include supernet routes
has to be configured globally on the router

Explanation: No answer description available for this question

Discussion

Q33. Question

Explanation: No answer description available for this question

Discussion

Q34. Question

Explanation: No answer description available for this question

Discussion

Q35. In which IOS CLI mode must a network administrator issue the maximum-paths command to configure load balancing in EIGRP?

global configuration mode
interface configuration mode
privileged mode
router configuration mode

Explanation: No answer description available for this question

Discussion

Q36. Two routers, R1 and R2, share a 64 kb/s link. An administrator wants to limit the bandwidth used by EIGRP between these two routers to 48 kb/s. Which command is used on both routers to configure the new bandwidth setting?

ip bandwidth-percent eigrp 100 48
ip bandwidth-percent eigrp 64 48
ip bandwidth-percent eigrp 100 64
ip bandwidth-percent eigrp 100 75
ip bandwidth-percent eigrp 75 100

Explanation: No answer description available for this question

Discussion

Q37. Question

Explanation: No answer description available for this question

Discussion

Q38. Refer to the exhibit. A network administrator has configured EIGRP authentication between routers R1 and R2. After the routing tables are reviewed, it is noted that neither router is receiving EIGRP updates. What is a possible cause for this failure?

The same key chain name must be used on each router.
The same number of key strings must be used on each router.
The key string should be used in interface mode instead of the key chain.
The same autonomous system numbers must be used in the interface configurations of each router.
The authentication configuration is correct, issue the show ip eigrp neighbors command to troubleshoot the issue.

Explanation: No answer description available for this question

Discussion

Q39. Two routers, R1 and R2, have established an EIGRP neighbor relationship, but there is still a connectivity problem. Which issue could be causing this problem?

an authentication mismatch
an access list that is blocking advertisements from other networks
automatic summarization that is disabled on both routers
a process ID mismatch

Explanation: No answer description available for this question

Discussion

Q40. Question

Explanation: No answer description available for this question

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Q41. Question

Explanation: No answer description available for this question

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Q42. Question

Explanation: No answer description available for this question

Discussion

Q43. Fill in the blank. Do not use abbreviations.

The passive-interface command causes an EIGRP router to stop sending hello packets through an interface.

Explanation: No answer description available for this question

Discussion

Q44. What is the purpose of a Null0 route in the routing table?

to redistribute external routes into EIGRP
to prevent routing loops
to act as a gateway of last resort
to prevent the router from sending EIGRP packets

Explanation: No answer description available for this question

Discussion

Q45. Which administrative distance is used to advertise routes learned from other protocols that are redistributed into EIGRP?

170
90
115
5

Explanation: Routes learned from other routing protocols that are redistributed into EIGRP are known as external routes and are assigned an administrative distance of 170.

Discussion

Q46. Question

Explanation: No answer description available for this question

Discussion

Q47. Which command would limit the amount of bandwidth that is used by EIGRP for protocol control traffic to approximately 128 Kb/s on a 1.544 Mb/s link?

ip bandwidth-percent eigrp 100 8
maximum-paths 8
variance 8
traffic-share balanced

Explanation: No answer description available for this question

Discussion

Q48. By default, how many equal-cost routes to the same destination network will EIGRP install in the routing table?

Explanation: No answer description available for this question

Discussion

Q49. Question

Explanation: No answer description available for this question

Discussion

Q50. What two statements are correct regarding EIGRP authentication? (Choose two.)

EIGRP authentication uses the MD5 algorithm.
EIGRP authentication uses a pre-shared key.
EIGRP authentication requires that both routers have the same key chain name.
EIGRP authentication uses varying levels of WEP to encrypt data exchanged between routers.
EIGRP authentication can be configured on one router and updates from this router are protected; whereas a neighbor router can be without the authentication configuration and its updates are unprotected.

Explanation: No answer description available for this question

Discussion

Q51. Which EIGRP parameter must match between all routers forming an EIGRP adjacency?

hello timer
variance
autonomous system number
hold timer
administrative distance

Explanation: EIGRP routers must belong to the same autonomous system for an adjacency to be successful. The autonomous system number is specified at the end of the router command.

Discussion

Q52. Which command can be issued on a router to verify that automatic summarization is enabled?

show ip eigrp interfaces
show ip protocols
show ip interface brief
show ip eigrp neighbors

Explanation: No answer description available for this question

Discussion

Q53. Fill in the blank. Do not use abbreviations.

What is the command that should be issued on a router to verify that EIGRP adjacencies were formed? show ip eigrp neighbors

Explanation: No answer description available for this question

Discussion

Q54. Open the PT Activity. Perform the tasks in the activity instructions and then answer the question. R1 and R2 could not establish an EIGRP adjacency. What is the problem?

EIGRP is down on R1.
EIGRP is down on R2.
R1 Fa0/0 and R2 Fa0/0 are on different networks.
R1 Fa0/0 is not configured to send hello packets.
R1 Fa0/0 link local address is wrong.

Explanation: No answer description available for this question

Discussion

Q55. Question

Explanation: No answer description available for this question

Discussion

Q56. In which scenario will the use of EIGRP automatic summarization cause inconsistent routing in a network?

when there is no common subnet that exists between neighboring routers
when the routers in an IPv4 network have mismatching EIGRP AS numbers
when there is no adjacency that is established between neighboring routers
when the routers in an IPv4 network are connected to discontiguous networks with automatic summarization enabled

Explanation: No answer description available for this question

Discussion

Q57. Which OSPF data structure is identical on all OSPF routers that share the same area?

forwarding database
routing table
link-state database
adjacency database

Explanation: No answer description available for this question

Discussion

Q58. Which command will selectively display IPv6 routes that are learned from a remote network?

show ip route
show ipv6 route ospf
show ip route ospf
show ipv6 route

Explanation: No answer description available for this question

Discussion

CCNA 3 Chapter 8: Single-Area OSPF (v5.0.3 + v6.0) Exam Answers – 100% Result

Q1. By default, what is the OSPF cost for any link with a bandwidth of 100 Mb/s or greater?

Q2. Which command will verify that a router that is running OSPFv3 has formed an adjacency with other routers in its OSPF area?

Q3. Which OSPF component is identical in all routers in an OSPF area after convergence?

Q4. Which OPSF packet contains the different types of link-state advertisements?

Q5. Which three addresses could be used as the destination address for OSPFv3 messages? (Choose three.)

Q6. Fill in the blank.

Q7. What are the two purposes of an OSPF router ID? (Choose two.)

Q8. A network administrator enters the command ipv6 router ospf 64 in global configuration mode. What is the result of this command?

Q9. What happens immediately after two OSPF routers have exchanged hello packets and have formed a neighbor adjacency?

Q10. Open the PT Activity. Perform the tasks in the activity instructions and then complete the task. What message is displayed on www.ciscoville.com?

Q11. What are two reasons that will prevent two routers from forming an OSPFv2 adjacency? (Choose two.)

Q12. What does a Cisco router use automatically to create link-local addresses on serial interfaces when OSPFv3 is implemented?

Q13. Single area OSPFv3 has been enabled on a router via the ipv6 router ospf 20 command. Which command will enable this OSPFv3 process on an interface of that router?

Q14. Fill in the blank.

Q15. Which command will provide information specific to OSPFv3 routes in the routing table?

Q16. Which command should be used to check the OSPF process ID, the router ID, networks the router is advertising, the neighbors the router is receiving updates from, and the default administrative distance?

Q17. What is the metric that is used by OSPF?

Q18. What function is performed by the OSPF designated router?

Q19. What is used to create the OSPF neighbor table?

Q20. When a network engineer is configuring OSPFv3 on a router, which command would the engineer issue immediately before configuring the router ID?

Q21. What will an OSPF router prefer to use first as a router ID?

Q22. Question

Q23. Question

Q24. Question

Q25. Question

Q26. Question

Q27. Question

Q28. Question

Q29. Which three statements are advantages of using automatic summarization? (Choose three.)

Q30. Question

Q31. Which address best summarizes the IPv6 addresses 2001:DB8:ACAD::/48, 2001:DB8:9001::/48, and 2001:DB8:8752::/49?

Q32. What is a characteristic of manual route summarization?

Q33. Question

Q34. Question

Q35. In which IOS CLI mode must a network administrator issue the maximum-paths command to configure load balancing in EIGRP?

Q36. Two routers, R1 and R2, share a 64 kb/s link. An administrator wants to limit the bandwidth used by EIGRP between these two routers to 48 kb/s. Which command is used on both routers to configure the new bandwidth setting?

Q37. Question

Q38. Refer to the exhibit. A network administrator has configured EIGRP authentication between routers R1 and R2. After the routing tables are reviewed, it is noted that neither router is receiving EIGRP updates. What is a possible cause for this failure?

Q39. Two routers, R1 and R2, have established an EIGRP neighbor relationship, but there is still a connectivity problem. Which issue could be causing this problem?

Q40. Question

Q41. Question

Q42. Question

Q43. Fill in the blank. Do not use abbreviations.

Q44. What is the purpose of a Null0 route in the routing table?

Q45. Which administrative distance is used to advertise routes learned from other protocols that are redistributed into EIGRP?

Q46. Question

Q47. Which command would limit the amount of bandwidth that is used by EIGRP for protocol control traffic to approximately 128 Kb/s on a 1.544 Mb/s link?

Q48. By default, how many equal-cost routes to the same destination network will EIGRP install in the routing table?

Q49. Question

Q50. What two statements are correct regarding EIGRP authentication? (Choose two.)

Q51. Which EIGRP parameter must match between all routers forming an EIGRP adjacency?

Q52. Which command can be issued on a router to verify that automatic summarization is enabled?

Q53. Fill in the blank. Do not use abbreviations.

Q54. Open the PT Activity. Perform the tasks in the activity instructions and then answer the question. R1 and R2 could not establish an EIGRP adjacency. What is the problem?​

Q55. Question

Q56. In which scenario will the use of EIGRP automatic summarization cause inconsistent routing in a network?

Q57. Which OSPF data structure is identical on all OSPF routers that share the same area?

Q58. Which command will selectively display IPv6 routes that are learned from a remote network?

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Q54. Open the PT Activity. Perform the tasks in the activity instructions and then answer the question. R1 and R2 could not establish an EIGRP adjacency. What is the problem?