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Cisco OSPF Command and Configuration Handbook

Book Description

The comprehensive, hands-on guide to all Cisco IOS Software OSPF commands

  • Stands as the complete OSPF command reference -- invaluable for network designers, engineers, and architects

  • Provides configuration, troubleshooting, and verification scenarios for every possible OSPF command supported by Cisco IOS Software that can be implemented on a minimum number of routers

  • Groups OSPF commands by area of implementation -- area configuration, redistribution, neighbor relationships, and route filtering, just to name a few

  • Provides clear and concise commentary on the initial release, purpose, syntax, and usage of each OSPF command

  • Offers excellent CCIE certification preparation from one of the CCIE Program Managers

  • Constructed as a portable field guide with easily navigable content so you can quickly find the information you need when you need it

As one of the most predominantly deployed Interior Gateway Protocols, Open Shortest Path First (OSPF) demands a wealth of knowledge on the part of internetworking professionals working with it on a daily basis. Unfortunately, publicly available documentation on the OSPF command set varies from being too thin on coverage to being too demanding on the required equipment needed to test what the documentation covers.

Cisco OSPF Command and Configuration Handbook is a clear, concise, and complete source of documentation for all Cisco IOS Software OSPF commands. The way you use this book will depend on your objectives. If you are preparing for the CCIE written and lab exams, then this book can be used as a laboratory guide to learn the purpose and proper use of every OSPF command. If you are a network designer, then this book can be used as a ready reference for any OSPF command.

Cisco OSPF Command and Configuration Handbook provides example scenarios that demonstrate the proper use of every OSPF command that can be implemented on a minimum number of routers. This will enable you to learn each command without requiring an extensive and expensive lab configuration. The scenarios clearly present the purpose and use of each command. Some of the examples lead you into common non-working situations in order to reinforce the understanding of the operation of the particular OSPF command.

Author Bill Parkhurst provides concise snapshots of every command with regard to command purpose, usage, syntax explanation, initial introduction in Cisco IOS Software, and cross references to related commands also covered in the book. This book covers many OSPF topic areas, including interface configuration, OSPF area configuration, route filtering, OSPF process configuration, route cost, default route generation, redistribution, administrative distance, OSPF neighbor relationships, route summarization, and show, debug, and clear commands.

Table of Contents

  1. Cisco OSPF Command and Configuration Handbook
    1. About the Author
      1. About the Technical Reviewers
    2. Acknowledgments
    3. Introduction
      1. Recommended Reading
      2. Icons Used in This Book
      3. Command Syntax Conventions
    4. 1. OSPF Process Configuration Commands
        1. 1-1. router ospf process-id
          1. Configuration Example: Enabling an OSPF Process
            1. Verification
            2. Troubleshooting
        2. 1-2. router ospf process-id vrf name
    5. 2. OSPF Area Commands
        1. 2-1. area area-id authentication
          1. Configuration Example: Simple Password Authentication
            1. Verification
            2. Troubleshooting
        2. 2-2. area area-id authentication message-digest
          1. Configuration Example 1: MD5 Password Authentication
            1. Verification
          2. Configuration Example 2: Changing Keys and Passwords
            1. Troubleshooting
        3. 2-3. area area-id default-cost cost
          1. Configuration Example: Setting the Default Cost for a Stub Area
            1. Verification
            2. Troubleshooting
        4. 2-4. area area-id nssa
          1. Configuration Example: Configuring an OSPF NSSA
            1. Verification
            2. Troubleshooting
        5. 2-5. area area-id nssa default-information-originate
          1. Configuration Example: Advertising an OSPF NSSA Default Route into an OSPF NSSA
            1. Verification
            2. Troubleshooting
        6. 2-6. area area-id nssa no-redistribution
          1. Configuration Example: Preventing Redistributed Routes from Entering an OSPF NSSA
            1. Verification
            2. Troubleshooting
        7. 2-7. area area-id nssa no-summary
          1. Configuration Example: Creating a Totally Stubby NSSA
            1. Verification
            2. Troubleshooting
        8. 2-8. area area-id range ip-address mask
        9. 2-9. area area-id range ip-address mask advertise
        10. 2-10. area area-id range ip-address mask not-advertise
          1. Configuration Example 1: Summarizing OSPF Routes from a Non-zero OSPF Area into the Backbone
            1. Verification
          2. Configuration Example 2: Summarizing OSPF Routes from Area 0 into a Non-zero OSPF Area
            1. Verification
          3. Configuration Example 3: Using a Static Route to Null 0 for the Summary Address
            1. Troubleshooting
        11. 2-11. area area-id stub
          1. Configuration Example: Configuring an OSPF Stub Area
            1. Verification
            2. Troubleshooting
        12. 2-12. area area-id stub no-summary
          1. Configuration Example: Configuring an OSPF Totally Stubby Area
            1. Verification
            2. Troubleshooting
        13. 2-13. area transit-area-id virtual-link router-id
          1. Configuration Example: Creating an OSPF Virtual Link
            1. Verification
            2. Troubleshooting
        14. 2-14. area transit-area-id virtual-link router-id authentication authentication-key password
        15. 2-15. area transit-area-id virtual-link router-id authentication message-digest
        16. 2-16. area transit-area-id virtual-link router-id authentication null
          1. Configuration Example 1: Simple Password Authentication Over a Virtual Link
            1. Verification
          2. Configuration Example 2: MD5 Authentication Over a Virtual Link
            1. Verification
          3. Configuration Example 3: Changing Keys and Passwords
            1. Verification
          4. Configuration Example 4: Null Authentication
            1. Verification
            2. Troubleshooting
        17. 2-17. area transit-area-id virtual-link router-id authentication-key password
          1. Configuration Example 1: Simple Password Authentication Over a Virtual Link
            1. Verification
            2. Troubleshooting
        18. 2-18. area transit-area-id virtual-link router-id dead-interval seconds
          1. Configuration Example: Modifying the Dead Interval Over a Virtual Link
            1. Verification
            2. Troubleshooting
        19. 2-19. area transit-area-id virtual-link router-id hello-interval seconds
          1. Configuration Example: Modifying the Hello Interval Over a Virtual Link
            1. Verification
            2. Troubleshooting
        20. 2-20. area transit-area-id virtual-link router-id message-digest-key key-id md5 password
          1. Configuration Example 1: Message Digest Authentication Over a Virtual Link
            1. Verification
          2. Configuration Example 2: Changing Keys and Passwords
            1. Verification
            2. Troubleshooting
        21. 2-21. area transit-area-id virtual-link router-id retransmit-interval seconds
          1. Configuration Example: Modifying the Retransmit Interval Over a Virtual Link
            1. Verification
            2. Verification
            3. Troubleshooting
        22. 2-22. area transit-area-id virtual-link router-id transmit-delay seconds
          1. Configuration Example: Modifying the Transmit Delay Value for a Virtual Link
            1. Verification
            2. Troubleshooting
    6. 3. Auto Cost
        1. 3-1. auto-cost reference-bandwidth bandwidth
          1. Configuration Example: Globally Modifying OSPF Interface Costs
            1. Verification
            2. Troubleshooting
    7. 4. Default Route Generation
        1. 4-1. default-information originate
          1. Configuration Example: Advertising a Default Route into the OSPF Domain
            1. Verification
            2. Troubleshooting
        2. 4-2. default-information originate always
          1. Configuration Example: Unconditionally Advertising a Default Route into the OSPF Domain
            1. Verification
            2. Troubleshooting
        3. 4-3. default-information originate metric cost
        4. 4-4. default-information originate always metric cost
          1. Configuration Example: Unconditionally Advertising a Default Route into the OSPF Domain
            1. Verification
            2. Troubleshooting
        5. 4-5. default-information originate metric-type type
        6. 4-6. default-information originate always metric-type type
          1. Configuration Example: Setting the OSPF Metric Type for a Default Route
            1. Verification
            2. Troubleshooting
        7. 4-7. default-information originate route-map route-map-name
          1. Configuration Example: Using a Route Map for Conditional Default Route Advertisement
            1. Verification
            2. Troubleshooting
    8. 5. Setting the Default Metric for Redistributed Protocols
        1. 5-1. default-metric cost
          1. Configuration Example: Setting the Default Cost for Redistributed Routes
            1. Verification
            2. Troubleshooting
    9. 6. Administrative Distance
        1. 6-1. distance administrative-distance
          1. Configuration Example: Adjusting the Administrative Distance to Influence Route Selection
            1. Verification
            2. Troubleshooting
        2. 6-2. distance administrative-distance source-ip-address source-ip-mask
        3. 6-3. distance administrative-distance source-ip-address source-ip-mask access-list-number
          1. Configuration Example 1: Adjusting the Administrative Distance of All Routes Learned from a Particular OSPF Neighbor
            1. Verification
          2. Configuration Example 2: Adjusting the Administrative Distance of Selected Routes Learned from a Particular OSPF Neighbor
            1. Verification
            2. Troubleshooting
        4. 6-4. distance ospf external administrative-distance
        5. 6-5. distance ospf inter-area administrative-distance
        6. 6-6. distance ospf intra-area administrative-distance
          1. Configuration Example: Adjusting the Administrative Distance Based on the Type of OSPF Route
            1. Verification
            2. Troubleshooting
    10. 7. Filtering Routes with Distribute Lists
        1. 7-1. distribute-list access-list-number in
          1. Configuration Example: Preventing OSPF Learned Routes from Being Installed in the IP Routing Table
            1. Verification
            2. Troubleshooting
        2. 7-2. distribute-list access-list-number in interface-type interface-number
          1. Configuration Example: Preventing Routes Learned via OSPF Over a Specific Interface from Being Installed in the IP Routing Table
            1. Verification
            2. Troubleshooting
        3. 7-3. distribute-list access-list-number out
        4. 7-4. distribute-list access-list-number out interface-type interface-number
        5. 7-5. distribute-list access-list-number out routing-process
          1. Configuration Example: Preventing Routes Redistributed into OSPF from Being Installed in the IP Routing Table
            1. Verification
            2. Troubleshooting
        6. 7-6. distribute-list access-list-name in
          1. Configuration Example: Preventing OSPF Learned Routes from Being Installed in the IP Routing Table
            1. Verification
            2. Troubleshooting
        7. 7-7. distribute-list access-list-name in interface-type interface-number
          1. Configuration Example: Preventing Routes Learned via OSPF Over a Specific Interface from Being Installed in the IP Routing Table
            1. Verification
            2. Troubleshooting
        8. 7-8. distribute-list access-list-name out
        9. 7-9. distribute-list access-list-name out interface-type interface-number
        10. 7-10. distribute-list access-list-name out routing-process
          1. Configuration Example: Preventing Routes Redistributed into OSPF from Being Installed in the OSPF Database
            1. Verification
            2. Troubleshooting
        11. 7-11. distribute-list prefix prefix-list-name in
          1. Configuration Example: Preventing OSPF Learned Routes from Being Installed in the IP Routing Table
            1. Verification
            2. Troubleshooting
        12. 7-12. distribute-list prefix prefix-list-name in interface-type interface-number
          1. Configuration Example: Preventing Routes Learned via OSPF Over a Specific Interface from Being Installed in the IP Routing Table
            1. Verification
            2. Troubleshooting
        13. 7-13. distribute-list prefix prefix-list-name out
        14. 7-14. distribute-list prefix prefix-list-name out interface-type interface-number
        15. 7-15. distribute-list prefix prefix-list-name out routing-process
          1. Configuration Example: Preventing Routes Redistributed into OSPF from Being Installed in the OSPF Database
            1. Verification
            2. Troubleshooting
    11. 8. Handling of MOSPF LSAs
        1. 8-1. ignore lsa mospf
    12. 9. Logging OSPF Neighbor Changes
        1. 9-1. log-adjacency-changes
        2. 9-2. log adjacency-changes detail
          1. Configuration Example 1: Enabling OSPF Neighbor Status-Change Logging to the Console
            1. Verification
          2. Configuration Example 2: Enabling OSPF Neighbor Status-Change Logging to Memory
            1. Verification
            2. Troubleshooting
    13. 10. Multiple Path Configuration
        1. 10-1. maximum-paths number-of-paths
          1. Configuration Example: Setting the Maximum Number of Equal-Cost Paths That OSPF Will Install in the IP Routing Table
            1. Verification
            2. Troubleshooting
    14. 11. OSPF neighbor Commands
        1. 11-1. neighbor ip-address
          1. Configuration Example 1: Using the neighbor Command to Enable OSPF on an NBMA
            1. Verification
          2. Configuration Example 2: Configuring OSPF Neighbors on a Hub and Spoke Topology with the Neighbors on the Same IP Subnet
            1. Verification
          3. Configuration Example 3: Configuring OSPF Neighbors on a Hub and Spoke Topology with the Neighbors on Different IP Subnets
            1. Verification
            2. Troubleshooting
        2. 11-2. neighbor ip-address cost cost
          1. Configuration Example: Modifying the Cost of an OSPF Neighbor on a Point-to-Multipoint Interface
            1. Verification
            2. Troubleshooting
        3. 11-3. neighbor ip-address database-filter all out
          1. Configuration Example: Reducing the Flooding of LSAs on a Redundant OSPF Link
            1. Verification
            2. Troubleshooting
        4. 11-4. neighbor ip-address poll-interval interval
          1. Configuration Example: Setting the Poll Interval on an NBMA Network
            1. Verification
            2. Troubleshooting
        5. 11-5. neighbor ip-address priority priority
          1. Configuration Example: Setting the Priority of an OSPF Neighbor
            1. Verification
            2. Troubleshooting
    15. 12. OSPF network Command
        1. 12-1. network ip-address wild-card-mask area area-id
          1. Configuration Example 1: Using a Host Address to Enable OSPF on an Interface
            1. Verification
          2. Configuration Example 2: Using the Same Network/Mask Pair in the OSPF network Statement That Is Used for the Interface
            1. Verification
          3. Configuration Example 3: Using a Shorter Mask to Enable OSPF on Multiple Interfaces
            1. Troubleshooting
    16. 13. Passive OSPF Interfaces
        1. 13-1. passive-interface interface-name interface-number
          1. Configuration Example: Using a Passive Interface to Reduce Protocol Traffic
            1. Verification
            2. Troubleshooting
        2. 13-2. passive-interface default
          1. Configuration Example: Many Interfaces, Few Neighbors
            1. Verification
            2. Troubleshooting
    17. 14. Route Redistribution
        1. 14-1. redistribute routing-process process-id
        2. 14-2. redistribute routing-process process-id metric ospf-metric
        3. 14-3. redistribute routing-process process-id metric-type metric-type
        4. 14-4. redistribute routing-process process-id subnets
        5. 14-5. redistribute routing-process process-id tag tag-value
          1. Configuration Example 1: Redistributing Classful Routes into OSPF with the Default Type and Metric
            1. Verification
          2. Configuration Example 2: Redistributing Classful Routes into OSPF with the Default Type and Specific Metric
            1. Verification
          3. Configuration Example 3: Redistributing Classful Routes into OSPF as Type 1 Routes Using a Specific Metric
            1. Verification
          4. Configuration Example 4: Redistributing Subnet Routes into OSPF as Type 1 Routes Using a Specific Metric
            1. Verification
          5. Configuration Example 5: Redistributing Subnet Routes into OSPF as Type 1 Routes Using a Specific Metric and Route Tag
            1. Verification
            2. Troubleshooting
        6. 14-6. redistribute routing-process process-id route-map route-map-name
          1. Configuration Example 1: Controlling the Routes to Be Redistributed Based on IP Address
            1. Verification
          2. Configuration Example 2: Modifying the Metric of Redistributed Routes Using a Route Map
            1. Verification
          3. Configuration Example 3: Modifying the Metric Type of Redistributed Routes Using a Route Map
            1. Verification
          4. Configuration Example 4: Modifying the Tag Value of Redistributed Routes Using a Route Map
            1. Verification
          5. Configuration Example 5: Controlling Route Redistribution Based on Tag Values
            1. Verification
            2. Troubleshooting
    18. 15. Controlling the OSPF Router ID
        1. 15-1. router-id ip-address
          1. Configuration Example: OSPF Router ID Selection
            1. Verification
            2. Troubleshooting
    19. 16. Summarizing External Routes
        1. 16-1. summary-address ip-address mask
        2. 16-2. summary-address ip-address mask not-advertise
          1. Configuration Example 1: Summarizing Routes Redistributed into OSPF
            1. Verification
            2. Troubleshooting
        3. 16-3. summary-address ip-address mask tag value
          1. Configuration Example 1: Attaching a Tag to Summarized Routes Created on an ASBR
            1. Verification
          2. Configuration Example 2: Using the Tag Value to Control Route Redistribution
            1. Verification
            2. Troubleshooting
    20. 17. OSPF Timers
        1. 17-1. timers lsa-group-pacing seconds
          1. Configuration Example: Modifying the LSA Group Pacing
            1. Verification
        2. 17-2. timers spf delay interval
          1. Configuration Example: Modifying the LSA Group Pacing
            1. Verification
    21. 18. Traffic Sharing
        1. 18-1. traffic-share min across-interfaces
    22. 19. Interface Configuration Commands
        1. 19-1. ip ospf authentication
        2. 19-2. ip ospf authentication authentication-key password
        3. 19-3. ip ospf authentication message-digest
        4. 19-4. ip ospf authentication null
          1. Configuration Example 1: Simple Password Authentication on an OSPF Network
            1. Verification
          2. Configuration Example 2: MD5 Authentication on an OSPF Network
            1. Verification
          3. Configuration Example 3: Changing Keys and Passwords
            1. Verification
          4. Configuration Example 4: Null Authentication
            1. Verification
            2. Troubleshooting
        5. 19-5. ip ospf cost cost
          1. Configuration Example: Modifying the OSPF Cost of an Interface
            1. Verification
            2. Troubleshooting
        6. 19-6. ip ospf database-filter all out
          1. Configuration Example: Reducing the Flooding of LSAs on a Redundant OSPF Link
            1. Verification
            2. Troubleshooting
        7. 19-7. ip ospf dead-interval seconds
          1. Configuration Example: Modifying the Interface Dead Interval
            1. Verification
            2. Troubleshooting
        8. 19-8. ip ospf demand-circuit
          1. Configuration Example: Configuring a Point-to-Point Link as an OSPF Demand Circuit
            1. Verification
            2. Troubleshooting
        9. 19-9. ip ospf flood-reduction
          1. Configuration Example: Configuring OSPF Flood Reduction on an Interface
            1. Verification
            2. Troubleshooting
        10. 19-10. ip ospf hello-interval seconds
          1. Configuration Example: Modifying the Interface Hello Interval
            1. Verification
            2. Troubleshooting
        11. 19-11. ip ospf message-digest-key key-id md5 password
          1. Configuration Example 1: Message Digest Authentication on an OSPF Interface
            1. Verification
          2. Configuration Example 2: Changing Keys and Passwords
            1. Verification
            2. Troubleshooting
        12. 19-12. ip ospf mtu-ignore
          1. Configuration Example: OSPF Adjacency and MTU Mismatch
            1. Verification
            2. Troubleshooting
        13. 19-13. ip ospf network broadcast
          1. Configuration Example 1: Fully-meshed OSPF Neighbors on an NBMA Network
            1. Verification
          2. Configuration Example 2: Partially-meshed OSPF Neighbors on an NBMA Network
            1. Verification
            2. Troubleshooting
        14. 19-14. ip ospf network non-broadcast
        15. 19-15. ip ospf network point-to-multipoint
        16. 19-16. ip ospf network point-to-multipoint non-broadcast
          1. Configuration Example 1: Multipoint Hub with Point-to-Point Spokes
            1. Verification
          2. Configuration Example 2: Partially Meshed Hub and Spoke Using a Multipoint Network
            1. Verification
            2. Troubleshooting
        17. 19-17. ip ospf network point-to-point
          1. Configuration Example: Point-to-Point Partially Meshed OSPF Neighbors
            1. Verification
            2. Troubleshooting
        18. 19-18. ip ospf priority priority
          1. Configuration Example: Influencing the Election of the Designated Router
            1. Verification
            2. Troubleshooting
        19. 19-19. ip ospf retransmit-interval seconds
          1. Configuration Example: Modifying the Retransmit Interval
            1. Verification
            2. Troubleshooting
        20. 19-20. ip ospf transmit-delay seconds
          1. Configuration Example: Modifying the Transmit Delay Value for an OSPF Interface
            1. Verification
            2. Troubleshooting
    23. 20. show Commands
        1. 20-1. show ip ospf
        2. 20-2. show ip ospf process-id
          1. Example: Displaying OSPF Process Information
        3. 20-3. show ip ospf border-routers
        4. 20-4. show ip ospf process-id border-routers
          1. Example: Displaying OSPF Border Router Information
        5. 20-5. show ip ospf database
        6. 20-6. show ip ospf process-id database
        7. 20-7. show ip ospf database adv-router router-id
        8. 20-8. show ip ospf process-id database adv-router router-id
        9. 20-9. show ip ospf database asbr-summary
        10. 20-10. show ip ospf process-id database asbr-summary
        11. 20-11. show ip ospf database asbr-summary asbr-id
        12. 20-12. show ip ospf process-id database asbr-summary asbr-id
        13. 20-13. show ip ospf database database-summary
        14. 20-14. show ip ospf process-id database database-summary
        15. 20-15. show ip ospf database external
        16. 20-16. show ip ospf process-id database external
        17. 20-17. show ip ospf database network
        18. 20-18. show ip ospf process-id database network
        19. 20-19. show ip ospf database nssa-external
        20. 20-20. show ip ospf process-id database nssa-external
        21. 20-21. show ip ospf database router
        22. 20-22. show ip ospf process-id database router
        23. 20-23. show ip ospf database self-originate
        24. 20-24. show ip ospf process-id database self-originate
        25. 20-25. show ip ospf database summary
        26. 20-26. show ip ospf process-id database summary
          1. Example 1: Displaying OSPF Database Information from a Specific OSPF Router
          2. Example 2: Displaying OSPF Database Information from an OSPF ASBR Router
        27. 20-27. show ip ospf flood-list
        28. 20-28. show ip ospf process-id flood-list
        29. 20-29. show ip ospf flood-list int-name int-number
        30. 20-30. show ip ospf process-id flood-list int-name int-number
          1. Example: Displaying All OSPF Floodlist Information
        31. 20-31. show ip ospf interface
        32. 20-32. show ip ospf process-id interface
        33. 20-33. show ip ospf interface int-name int-number
        34. 20-34. show ip ospf process-id interface int-name int-number
          1. Example 1: Displaying Information for an OSPF-Enabled Interface
          2. Example 2: Displaying OSPF Timer Information for an OSPF-enabled Interface
        35. 20-35. show ip ospf neighbor
        36. 20-36. show ip ospf process-id neighbor
        37. 20-37. show ip ospf neighbor neighbor-id
        38. 20-38. show ip ospf process-id neighbor neighbor-id
        39. 20-39. show ip ospf neighbor int-name int-number
        40. 20-40. show ip ospf process-id neighbor int-name int-number
        41. 20-41. show ip ospf neighbor detail
        42. 20-42. show ip ospf process-id neighbor detail
        43. 20-43. show ip ospf neighbor detail neighbor-id
        44. 20-44. show ip ospf process-id neighbor detail neighbor-id
        45. 20-45. show ip ospf neighbor int-name int-number
        46. 20-46. show ip ospf process-id neighbor int-name int-number
          1. Example 1: Displaying Information for All OSPF Neighbors
          2. Example 2: Displaying Detailed Information for a Specific OSPF Neighbor
        47. 20-47. show ip ospf request-list
        48. 20-48. show ip ospf process-id request-list
        49. 20-49. show ip ospf request-list neighbor-id
        50. 20-50. show ip ospf process-id request-list neighbor-id
        51. 20-51. show ip ospf request-list int-name int-number
        52. 20-52. show ip ospf process-id request-list int-name int-number
          1. Example: Displaying Request List Information for a Particular OSPF Neighbor
        53. 20-53. show ip ospf retransmission-list
        54. 20-54. show ip ospf process-id retransmission-list
        55. 20-55. show ip ospf retransmission neighbor-id
        56. 20-56. show ip ospf process-id retransmission neighbor-id
        57. 20-57. show ip ospf retransmission int-name int-number
        58. 20-58. show ip ospf process-id retransmission int-name int-number
          1. Example: Displaying the List of LSAs Waiting to Be Re-sent on a Particular Interface
        59. 20-59. show ip ospf summary-address
        60. 20-60. show ip ospf process-id summary-address
          1. Example: Displaying the List of Summary Addresses Configured on a Router
        61. 20-61. show ip ospf virtual-links
        62. 20-62. show ip ospf process-id virtual-links
          1. Example: Displaying the Status of All Virtual Links Configured on the Local Router
    24. 21. debug Commands
        1. 21-1. debug ip ospf adj
          1. Example 1: Displaying the Successful Formation of an OSPF Adjacency
          2. Example 2: Displaying the Attempted Formation of an OSPF Adjacency when There Is an Area Mismatch
        2. 21-2. debug ip ospf events
          1. Example 1: Displaying the Successful Formation of an OSPF Adjacency
          2. Example 2: Debugging an OSPF Adjacency Problem
        3. 21-3. debug ip ospf flood
        4. 21-4. debug ip ospf flood ip-access-list-number
          1. Example 1: Displaying All Output from the OSPF Flooding Protocol
          2. Example 2: Selective Display of OSPF Protocol Debugging Output
        5. 21-5. debug ip ospf lsa-generation
        6. 21-6. debug ip ospf lsa-generation ip-access-list-number
          1. Example: Displaying the Successful Formation of an OSPF Adjacency
        7. 21-7. debug ip ospf packet
          1. Example: Displaying OSPF Packet Information
        8. 21-8. debug ip ospf retransmission
        9. 21-9. debug ip ospf spf
        10. 21-10. debug ip ospf spf external
        11. 21-11. debug ip ospf spf external access-list-number
        12. 21-12. debug ip ospf spf inter
        13. 21-13. debug ip ospf spf inter access-list-number
        14. 21-14. debug ip ospf spf intra
        15. 21-15. debug ip ospf spf intra access-list-number
          1. Example: Displaying SPF Output for External OSPF Routes
    25. 22. clear Commands
        1. 22-1. clear ip ospf counters
        2. 22-2. clear ip ospf process-id counters
        3. 22-3. clear ip ospf process-id counters neighbor
        4. 22-4. clear ip ospf process-id counters neighbor int-name int-number
          1. Example: Viewing and Clearing OSPF Neighbor State Transition Counters
        5. 22-5. clear ip ospf process
        6. 22-6. clear ip ospf process-id process
        7. 22-7. clear ip ospf redistribution
        8. 22-8. clear ip ospf process-id redistribition