CCNA 3 Chapter 9 Exam Answers

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Exam Chapter 9 Questions and Answers CCNA 3 V6.0

A network administrator is verifying a multi-area OSPF configuration by checking the routing table on a router in area 1. The administrator notices a route to a network that is connected to a router in area 2. Which code appears in front of this route in the routing table within area 1?

In a routing table, a route with the code O IA indicates a network that is learned from another area and received by the ABR as an external LSA. The ABR has flooded the route into its area so that internal routers may add it to their databases. Label C would indicate a network that is directly connected to an interface on the router. Label O would indicate a network that is advertised by another router in the same area. Label O E2 would indicate an external network (non-OSPF network) that is advertised by an ASBR.

Open the PT Activity. Perform the tasks in the activity instructions and then answer the question.
Why are users in the OSPF network not able to access the Internet?

The configuration of the redistribution of the default route on the router R1 is correct. The interface that is located between the router R1 and the ISP is operational. The OSPF timers of the routers R1, R2, and R3 are set to default. The network statement on router R1 contains an error in the network address.

Match each type of OSPF router to its description. (Not all options are used.)

Multiarea OSPF networks use four types of routers: internal router, backbone router, Area Border Router (ABR), and Autonomous System Boundary Router (ASBR). Their roles depend upon the location and function of their interfaces. They all participate in OSPF routing. In addition, an ASBR can participate in other routing protocols and import non-OSPF network information to the OSPF network.

Refer to the exhibit. What can be concluded about network 192.168.4.0 in the R2 routing table?

In a routing table, a route with the label O indicates a network that is advertised by another router in the same area. In this case, the exit interface is GigabitEthernet0/1. The designation O IA means the entry was learned from an interarea LSA that was generated from an ABR. Label O*E2 indicates an external network. In this case, the network designation of 0.0.0.0/0 indicates that this external network is the default route for all traffic that goes to external networks.

Refer to the exhibit. Which two statements are correct? (Choose two.)

The entry for 172.16.200.1 represents a local interface, not a loopback interface. There are two routes that are O IA, meaning that these are interarea routes. To reach network 172.16.2.0, traffic would exit via the Serial0/0/0 interface, not the GigabitEthernet0/0 interface. The routing table contains more than two intra-area routes. To reach network 192.168.1.0, traffic would exit via the Serial0/0/0 interface.

Which two networks are part of the summary route 192.168.32.0/22? (Choose two.)

The summary route 192.168.32.0/22 would include networks 192.168.32.0/24, 192.168.33.0/24, 192.168.34.0/24, and 192.168.35.0/24.

Refer to the exhibit. What is indicated by the O IA in the router output?

The O IA in the routing table indicates that those routes were learned from other areas. The O indicates OSPF, and the IA indicates interarea routes that were received as summary LSAs.

Refer to the exhibit. Fill in the blank. Do not use abbreviations.
The __ command must be issued to configure R1 for multiarea OSPF.​

The statement needs to contain the network 192.168.10.128 with a wildcard mask of 0.0.0.127. The area where this network is located is area 1.

Fill in the blank. Use a number.
A type ____ LSA identifies the ASBR and provides a route to it.

What is used to facilitate hierarchical routing in OSPF?

OSPF supports the concept of areas to prevent larger routing tables, excessive SPF calculations, and large LSDBs. Only routers within an area share link-state information. This allows OSPF to scale in a hierarchical fashion with all areas that connect to a backbone area.

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What OSPF LSA type is used to inform routers of the router ID of the DR in each multiaccess network in an OSPF area?

OSPF has many different LSA types.
type 1 – contains a list of directly connected interfaces
type 2 – only exists for multiaccess networks and includes DR router ID
type 3 – used by ABRs to advertise networks from other areas
type 4 – generated by ABRs to identify an ASBR and provide a route to it

Refer to the exhibit. A network administrator has been asked to summarize the networks shown in the exhibit as part of a multiarea OSPF implementation. All addresses are using a subnet mask of 255.255.255.0. What is the correct summarization for these eight networks?

The only correct summarization is 10.0.0.0 255.255.240.0. The binary calculation would be:
10.0.4.0 00001010.00000000.0000 0100.00000000
10.0.5.0 00001010.00000000.0000 0101.00000000
10.0.6.0 00001010.00000000.0000 0110.00000000
10.0.7.0 00001010.00000000.0000 0111.00000000
10.0.8.0 00001010.00000000.0000 1000.00000000
10.0.9.0 00001010.00000000.0000 1001.00000000
10.0.10.0 00001010.00000000.0000 1010.00000000
10.0.11.0 00001010.00000000.0000 1011.00000000
Determining the matching bits and then adding zeroes at the end results in a summary network address of 10.0.0.0; since 20 bits match, the mask would be /20.

Which three steps in the design and implementation of a multiarea OSPF network are considered planning steps? (Choose three.)

The best practice for implementing a multiarea OSPF network includes the steps: (1) Define the network requirements. (2) Gather the required parameters. (3) Define the OSPF parameters. (4) Configure OSPF. (5) Verify OSPF. Steps 1-3 are considered the planning steps in the process.

Which characteristic describes both ABRs and ASBRs that are implemented in a multiarea OSPF network?

ABRs and ASBRs need to perform any summarization or redistribution among multiple areas, and thus demand more router resources than a regular router in an OSPF area.

Which two statements correctly describe OSPF type 3 LSAs? (Choose two.)

Type 4 LSAs are known as autonomous system external LSA entries. Type 4 LSAs are generated by an ABR to inform other areas of next-hop information for the ASBR. Type 1 LSAs are known as router link entries. Type 3 LSAs can be generated without requiring a full SPF calculation. Type 3 LSAs are used to carry routes between OSPF areas.

What are two reasons for creating an OSPF network with multiple areas? (Choose two.)

If a router is not running OSPF, it is not configurable with an OSPF area. OSPF areas have no direct relationship with the Internet. Routers that run OSPF can connect to the Internet, but multiple OSPF areas are not required for this purpose. OSPF areas help to decrease the demand for router memory and processing power by limiting OSPF protocol traffic, keeping link-state databases small, and requiring fewer SPF recalculations. Multiarea OSPF requires additional steps to configure and therefore does not simplify the configuration process.

Fill in the blank. Use a number.
An ASBR generates type __ LSAs for each of its external routes and floods them into the area that it is connected to.

The network administrator has been asked to summarize the routes for a new OSPF area. The networks to be summarized are 172.16.8.0, 172.16.10.0, and 172.16.12.0 with subnet masks of 255.255.255.0 for each network. Which command should the administrator use to forward the summary route for area 15 into area 0?

Because all OSPF networks start with area 0, the new area would need to be anything but area 0, The correct option would be area 15 range 172.16.8.0 255.255.248.0 because this is the correct summarization of the networks in the new area 15. The summarization must come from area 15 to area 0, because all OSPF areas interconnect via area 0. The matching bits for the correct option, in binary, are:
172.16.8.0 10101100.00010000.00001 000.00000000
172.16.10.0 10101100.00010000.00001 010.00000000
172.16.12.0 10101100.00010000.00001 100.00000000

Fill in the blank. Do not use acronyms. OSPF type 2 LSA messages are only generated by the __ router to advertise routes in multiaccess networks.

Open the PT Activity. Perform the tasks in the activity instructions and then answer the question.
Fill in the blank. Do not use abbreviations.
What is the missing command on router R2 to establish an adjacency between routers R1 and R3?

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What type of OSPF LSA is originated by ASBR routers to advertise external routes?

OSPF has many different LSA types.
type 1 – contains a list of directly connected interfaces
type 2 – only exists for multiaccess networks and includes DR router ID
type 3 – used by ABRs to advertise networks from other areas
type 4 – generated by ABRs to identify an ASBR and provides a route to it
type 5 – originated by ASBRs to advertise external routes

What routing table descriptor is used to identify OSPF summary networks that originate from an ABR?

O – intra-area routes learned from a DR
O IA – summary interarea routes that are learned from a ABR
O E1 or O E2 – external routes that are learned from an ASBR


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