CCNA 3 Module 2 V3.1 Answers

1. What does OSPF use to calculate the cost to a destination network?

bandwidth

bandwidth and hop count

bandwidth and reliability

bandwidth, load, and reliablity

 

2. Which of the following should be considered when troubleshooting a problem with the establishment of neighbor relationships between OSPF routers? (Choose three.)

OSPF interval timers mismatch

gateway of last resort not redistributed

interface network type mismatch

no loopback interface configured

administrative distance mismatch

inconsistent authentication configuration

 

3. Which router is the root of an SPF tree?

border router

nearest neighboring router

local router

trunk router, as determined by the SPF algorithm

 

4. In which types of networks are OSPF DR elections necessary? (Choose two.)

point-to-point

point-to-multipoint

broadcast multiaccess

nonbroadcast multiaccess

 

5.

What will be the result of the DR and BDR elections for this single area OSPF network? (Choose three.)

HQ will be DR for 10.4.0.0/16.

Router A will be DR for 10.4.0.0/16.

HQ will be BDR for 10.4.0.0/16.

Router A will be DR for 10.5.0.0/16.

Remote will be DR for 10.5.0.0/16.

Remote will be BDR for 10.5.0.0/16.

 

6.

Refer to the network shown in the diagram. Which command sequence on RouterB will redistribute a Gateway of Last Resort to the other routers in OSPF area 0?

RouterB(config)# router ospf 10
RouterB(config-router)# gateway-of-last-resort 172.16.6.6

RouterB(config)# ip route 0.0.0.0 0.0.0.0 serial 0

RouterB(config)# ip route 0.0.0.0 0.0.0.0 172.16.6.6
RouterB(config)# router ospf 10
RouterB(config-router)# default-information originate

RouterB(config)# router ospf 10
RouterB(config-router)# default network 172.16.6.6 0.0.0.3 area 0

RouterB(config)# ip route 0.0.0.0 0.0.0.0 172.16.6.6

RouterB(config)# ip default-route 0.0.0.0 0.0.0.0 172.16.6.6
RouterB(config)# router ospf 10
RouterB(config-router)# redistribute ip default-route

 

7. Why is it difficult for routing loops to occur in networks that use link-state routing?

Each router builds a simple view of the network based on hop count.

Routers flood the network with LSAs to discover routing loops.

Each router builds a complete and synchronized view of the network.

Routers use hold-down timers to prevent routing loops.

 

8. What information can be obtained from the output of the show ip ospf interface command? (Choose three.)

link-state age intervals

timer intervals

router ID number

link-state update intervals

neighbor adjacencies

 

9.

RouterA, RouterB, and RouterC in the diagram are running OSPF on their Ethernet interfaces. Loopback interfaces (Lo 0) are configured as shown. What happens when RouterD is added to the network?

RouterB takes over as DR and RouterD becomes the BDR.

RouterD becomes the BDR and RouterA remains the DR.

RouterD becomes the DR and RouterA becomes the BDR.

RouterC acts as the DR until the election process is complete.

RouterD becomes the DR and RouterB remains the BDR.

There is no change in the DR or BDR until either current DR or BDR goes down.

 

10. What are the benefits of the hierarchical design approach that is used in large OSPF networks? (Choose three.)

reduction of routing overhead

increased routing overhead

faster convergence

slower convergence

distribution of network instability to all areas of the network

isolation of network instability to one area of the network

 

11.

Which command sequence will enable OSPF in the backbone area for the two Ethernet links on RouterA?

RouterA(config)# router ospf 1
RouterA(config-router)# network 172.16.4.0 0.0.1.255 area 1

RouterA(config)# router ospf 10
RouterA(config-router)# network 172.16.4.0 0.0.0.255 area 0
RouterA(config-router)# network 172.16.5.0 0.0.0.255 area 0

RouterA(config)# router ospf 10
RouterA(config-router)# area 0 network 172.16.4.0 0.0.1.255

RouterA(config)# router ospf 0
RouterA(config-route)# network 172.16.4.0 0.0.255.255 area 0

RouterA(config)# router ospf 0
RouterA(config-router)# network 172.16.4.0 255.255.255.0
RouterA(config-router)# network 172.16.5.0 255.255.255.0

RouterA(config)# router ospf 1
RouterA(config-router)# network 172.16.4.0 255.255.254.0 area 0

 

12. Which of the following are disadvantages of link-state routing? (Choose three.)

Link-state protocols require careful network design.

Link-state protocols are prone to routing loops.

Link-state hello updates can cause broadcast flooding.

Link-state protocols place significant demands on router processors and memory resources.

Link-state protocols require a knowledgeable network administrator.

Link-state protocols do not support Variable Length Subnet Masking.

 

13. What speeds up convergence in a network using link-state routing?

updates triggered by network changes

updates sent at regular intervals

updates sent only to directly connected neighbors

updates that include complete routing tables

 

14. Because of security concerns, a network administrator wants to set up authentication between two routers. Which of the following commands will configure Router_A to trust Router_B with a clear text password of apollo?

Router_A(config-if)# ospf authentication-key apollo

Router_A(config-if)# ip authentication-key apollo

Router_A(config-if)# ip ospf authentication apollo

Router_A(config-if)# ip ospf authentication-key apollo

 

15. How can the OSPF cost for a link be established? (Choose two.)

It is set to 1544 by default for all OSPF interfaces.

It can be set with the ip ospf cost command.

The configured loopback addresses map to link costs.

It is calculated proportionally to observed throughput capacity of the router.

It may be calculated using the formula 10⁸/bandwidth.

 

16. A network administrator has configured a default route on Router_A but it is not being shared with adjacent Router_B and the other routers in the OSPF area. Which command will save the administrator the time and trouble of configuring this default route on Router_B and all of the other routers in the OSPF area?

Router_A(config-router)# ospf redistribute default-route

Router_B(config-router)# ospf redistribute default-route

Router_A(config-router)# default-information originate

Router_B(config-router)# default-information originate

Router_A(config-router)# ip ospf update-default

Router_B(config-router)# ip ospf update-default

 

17.

The routers in the diagram are configured as shown. The loopback interface on router R1 is labeled as lo0. All OSPF priorities are set to the default except for Ethernet0 of router R2, which has an OSPF priority of 2. What will be the result of the OSPF DR/BDR elections on the 192.1.1.0 network? (Choose two.)

R1 will be the DR

R1 will be the BDR

R2 will be the DR

R2 will be the BDR

R3 will be the DR

R3 will be the BDR

 

18. Which router command will display the interface priority value and other key information for the OSPF configuration of the serial 0 interface?

router# show ospf serial 0

router# show interface serial 0 OSPF

router# show ip interface serial 0

router# show ip ospf interface serial 0

 

19. Which of the following are required when adding a network to the OSPF routing process configuration? (Choose three.)

network address

loopback address

autonomous system number

subnet mask

wildcard mask

area ID

 

20. What does OSPF use to reduce the number of exchanges of routing information in networks where large numbers of neighbors are present? (Choose two.)

root router

backup root router

domain router

backup domain router

designated router

backup designated router