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OSPF Implementation

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Feb 3, 2015.

Chapter Description

This chapter from Implementing Cisco IP Routing (ROUTE) Foundation Learning Guide: (CCNP ROUTE 300-101) examines the Open Shortest Path First (OSPF) Protocol, one of the most commonly used interior gateway protocols in IP networking.

Review Questions

Answer the following questions, and then see Appendix A, “Answers to Review Questions,” for the answers.

  1. What is the OSPF transport?

    1. IP/88
    2. TCP/179
    3. IP/89
    4. IP/86
    5. UDP/520
  2. An Area Border Router maintains _____.

    1. A single database for all areas
    2. A separate database for each area with which it is connected
    3. Two databases: one for the backbone and one for all other areas
    4. A separate routing table for each area
  3. Which two methods does OSPF employ to conserve the computing resources?

    1. Area-based segregation including stub areas
    2. LSDB
    3. Summarization
    4. Redistribution
    5. Network types
  4. What is the difference between an LSA 3 and an LSA 4?

    1. LSA 3 is a summary LSA, and LSA 4 is E1.
    2. LSA 3 is E1, and LSA 4 is a summary.
    3. LSA 3 is a summary for networks, and LSA 4 is a summary for ASBRs.
    4. LSA 3 is a summary for ASBRs, and LSA 4 is a summary for networks.
  5. Which two LSAs describe intra-area routing information?

    1. Summary
    2. External 1
    3. External 2
    4. Router
    5. Network
  6. An OSPF router receives an LSA and checks the sequence number of the LSA. This number matches the sequence number of an LSA that the receiving router already has. What does the receiving router do with the received LSA?

    1. Ignores the LSA
    2. Adds the LSA to the database
    3. Sends the newer LSU to the source router
    4. Floods the LSA to the other routers
  7. What are the two reasons why route summarization is important?

    1. Reduces LSA type 1 flooding
    2. Reduces LSA type 3 flooding
    3. Reduces the size of the routing table
    4. Reduces the size of the neighbor table
  8. Route summarization reduces the flooding of which two of the following LSA types?

    1. Router
    2. Network
    3. Summary
    4. External
    5. NSSA
  9. Stub area design can improve _____.

    1. CPU utilization on routers in the stub
    2. The number of adjacencies in the stub
    3. Ability to reach outside networks
    4. LSDB size on routers in the backbone
  10. Which feature characterizes both OSPFv2 and OSPFv3?

    1. Router ID in IPv4 format
    2. Router ID in IPv6 format
    3. Process activation using the network command
    4. The same LSA types
  11. Which address would you configure in the neighbor command to set up an OSPFv3 adjacency over an NBMA link?

    1. Local IPv4 address
    2. Neighbor’s IPv4 address
    3. Interface link local IPv6 address
    4. Local global IPv6 address
    5. Neighbor’s link-local IPv6 address
    6. Neighbor’s global IPv6 address
  12. You can run a single OSPFv3 process using the ipv6 router ospf command to support a support a dual-stack environment. (True or false?)

    1. True
    2. False
  13. Which of the following is not a characteristic of link-state routing protocols?

    1. They respond quickly to network changes.
    2. They broadcast every 30 minutes.
    3. They send triggered updates when a network change occurs.
    4. They may send periodic updates, known as link-state refresh, at long time intervals, such as every 30 minutes.
  14. Link-state routing protocols use a two-layer area hierarchy composed of which two areas?

    1. Backbone area
    2. Transmit area
    3. Regular area
    4. Linking area
  15. Which IPv4 address is used to send an updated LSA entry to OSPF DRs and BDRs?

    1. Unicast
    2. Unicast
    3. Multicast
    4. Multicast
  16. To ensure an accurate database, how often does OSPF flood (refresh) each LSA record?

    1. Every 60 minutes.
    2. Every 30 minutes.
    3. Every 60 seconds.
    4. Every 30 seconds.
    5. Flooding each LSA record would defeat the purpose of a link-state routing protocol, which strives to reduce the amount of routing traffic it generates.
  17. What kind of router generates LSA type 5 in a standard area?

    1. DR
    2. ABR
    3. ASBR
    4. ADR
  18. Where does a type 1 LSA flood to?

    1. To immediate peers
    2. To all other routers in the area where it originated
    3. To routers located in other areas
    4. To all areas
  19. How does a routing table reflect the link-state information of an intra-area route?

    1. The route is marked with O.
    2. The route is marked with I.
    3. The route is marked with IO.
    4. The route is marked with EA.
    5. The route is marked with O IA.
  20. Which type of external route is the default?

    1. E1.
    2. E2.
    3. E5.
    4. There is no default external route. OSPF adapts and chooses the most accurate one.
  21. How is the cost of an E1 external route calculated?

    1. The sum of the internal cost of each link the packet crosses
    2. The sum of the external cost and the internal cost of each link the packet crosses
    3. The external cost only
    4. The sum of all area costs, even those that are not used

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