M 1-2: OSPF Concepts and Config

Match the description to the term (not all are used). terms: -adjacency database -shortest path first -single-area OSPF -DUAL (not used) -link-state database -multiarea OSPF (not used)

*adjacency database*: this is where the details of the neighboring routers can be found *shortest path first*: this is the algorithm used by OSPF *single-area OSPF*: All the routers are in the backbone area *link-state database*: this is where you can find the topology table

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

0.0.0.127

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

0.0.0.255

An administrator is configuring single-area OSPF on a router. One of the networks that must be advertised is 128.107.0.0 255.255.255.192. 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

0.0.0.63

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

0.0.1.255

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

0.0.1.255

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

0.0.3.255

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

0.0.3.255

By default, what is the OSPF cost for any link with a bandwidth of 100 Mb/s or greater? 100000000 10000 1 100

1

What is the default router priority value for all Cisco OSPF routers? 0 1 10 255

1

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

192.168.1.100

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

65

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? 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.

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

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.

Configure a value using the router-id command.

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

HQ# clear ip ospf process

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.

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

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?​ 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. If the priority of router C is changed to 255, then it will become the DR.

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

Which three OSPF states are involved when two routers are forming an adjacency? (Choose three.) Exchange Init ExStart Two-way Loading Down

Init two-way down

Which three OSPF states are involved when two routers are forming an adjacency? (Choose three.) Init Down ExStart Loading Two-way Exchange

Init Down Two-way

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.

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

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.

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.

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.

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

Which OPSF packet contains the different types of link-state advertisements? hello DBD LSR LSU LSAck

LSU

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

R0-A

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

R1# show ip ospf interface serial0/0/1

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.) R2 will be elected DR. R1 will be elected BDR. R3 will be elected BDR. The R4 router ID is 172.16.1.1. The R4 FastEthernet 0/0 priority is 128. The router ID on R2 is the loopback interface.

R2 will be elected DR. R3 will be elected BDR. The R4 router ID is 172.16.1.1.

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.

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. 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.

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

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.

The R1 dead timer expires between hello packets from R2.

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

The R1 dead timer expires between hello packets from R2.

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.

The dead interval will now be 60 seconds.

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

The dead interval will now be 60 seconds.

What is a benefit of multiarea OSPF routing? Topology changes in one area do not cause SPF recalculations in other areas. Automatic route summarization occurs by default between 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.

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

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.

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

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

a 32-bit number formatted like an IPv4 address

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

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

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

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

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

building the topology table

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

choosing the best route

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

database description

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? link-state update link-state request database description link-state acknowledgment

database description

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

dead interval hello interval

Match each OSPF packet type to how it is used by a router. (Not all options are used.) terms: link-state update packet database description packet hello packet line-state request packet definitions: establish and maintain adjacencies advertise new info compare local topology to that sent by another router query another router additional info

establish and maintain adjacencies: hello packet advertise new info: link-state update packet compare local topology to that sent by another router: database description packet query another router additional info: line-state request packet

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

establishing neighbor adjacencies

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 mins every 10 mins every 30 mins every 60 mins

every 30 mins

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

every 30 minutes

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

exchanges link-state advertisements

Which step does an OSPF-enabled router take immediately after establishing an adjacency with another router? chooses the best path builds the topology table executes the SPF algorithm exchanges link-state advertisements

exchanges link-state advertisements

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

exchanging link-state advertisements

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

executing the SPF algorithm

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.) router ID hello interval dead interval router priority list of neighbors

hello interval dead interval

What indicates to a link-state router that a neighbor is unreachable? if the router no longer receives routing updates 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 hello packet

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

if the router no longer receives hello packets

Match the OSPF state with the order in which it occurs. (Not all options are used.) 1-7 state init state active state full state exchange state down state exstart state passive state two-way state loading state

init state: 2 full state: 7 exchange state: 5 down state: 1 exstart state: 4 two-way state: 3 loading state: 6

Which OSPF data structure is identical on all OSPF routers that share the same area? adjacency database link-state database routing table forwarding database

link-state database

Which OSPF data structure is identical on all OSPF routers that share the same area? forwarding database link-state database adjacency database routing table

link-state database

What type of address is 64.101.198.197? public private

public

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

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

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

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

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

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

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 neighbor show ip ospf interface serial 0/0/0 show ipv6 ospf interface serial 0/0/0 show ip ospf interface fastethernet 0/1

show ip ospf interface serial 0/0/0

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

show ip ospf interface serial 0/0/0

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

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

show ip protocols

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

the OSPF process ID on R1

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

the OSPF process ID on R1

What is used to facilitate hierarchical routing in OSPF? the use of multiple areas frequent SPF calculations autosummarization the election of designated routers

the use of multiple areas

What is used to facilitate hierarchical routing in OSPF? auto summarization the use of multiple areas frequent SPF calculations the election of designated routers

the use of multiple areas

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

to discover neighbors and build adjacencies between them

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

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

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

to uniquely identify the router within the OSPF domain to facilitate router participation in the election of the designated router

What are the two purposes of an OSPF router ID? (Choose two.) to facilitate the establishment of network convergence to uniquely identify the router within the OSPF domain to facilitate the transition of the OSPF neighbor state to Full 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 uniquely identify the router within the OSPF domain. to facilitate router participation in the election of the designated router.

In an OSPF network when are DR and BDR elections required? when all the routers in an OSPF area cannot form adjacencies when the two adjacent neighbors are in two different networks when the routers are interconnected over a common Ethernet network when the two adjacent neighbors are interconnected over a point-to-point link

when the routers are interconnected over a common Ethernet network

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 the routers are interconnected over a common Ethernet network