IP Routing: OSPF Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000)
OSPF Link-State Database Overload Protection
Downloads: This chapterpdf (PDF - 1.31MB) The complete bookPDF (PDF - 5.76MB) | The complete bookePub (ePub - 1.19MB) | Feedback

OSPF Link-State Database Overload Protection

OSPF Link-State Database Overload Protection

The OSPF Link-State Database Overload Protection feature allows you to limit the number of nonself-generated link-state advertisements (LSAs) for a given Open Shortest Path First (OSPF) process. Excessive LSAs generated by other routers in the OSPF domain can substantially drain the CPU and memory resources of the router.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for OSPF Link-State Database Overload Protection

It is presumed that you have OSPF running on your network.

Information About OSPF Link-State Database Overload Protection

Benefits of Using OSPF Link-State Database Overload Protection

The OSPF Link-State Database Overload Protection feature provides a mechanism at the OSPF level to limit the number of nonself-generated LSAs for a given OSPF process. When other routers in the network have been misconfigured, they may generate a high volume of LSAs, for instance, to redistribute large numbers of prefixes. This protection mechanism prevents routers from receiving a large number of LSAs and therefore experiencing CPU and memory shortages.

How OSPF Link-State Database Overload Protection Works

When the OSPF Link-State Database Overload Protection feature is enabled, the router keeps a count of the number of received (nonself-generated) LSAs that it has received. When the configured threshold number of LSAs is reached, an error message is logged. When the configured maximum number of LSAs is exceeded, the router will send a notification. If the count of received LSAs is still higher than the configured maximum after one minute, the OSPF process takes down all adjacencies and clears the OSPF database. In this ignore state, all OSPF packets received on any interface that belongs to this OSPF process are ignored and no OSPF packets are generated on any of these interfaces. The OSPF process remains in the ignore state for the time configured by the ignore-time keyword of the max-lsa command. Each time the OSPF process gets into an ignore state a counter is incremented. If this counter exceeds the number of minutes configured by the ignore-count keyword, the OSPF process stays permanently in the same ignore state and manual intervention is required to get the OSPF process out of the ignore state. The ignore state counter is reset to 0 when the OSPF process remains in the normal state of operation for the amount of time that was specified by the reset-time keyword.

If the warning-only keyword of the max-lsa command has been configured, the OSPF process will send only a warning that the LSA maximum has been exceeded.

How to Configure OSPF Link-State Database Overload Protection

Limiting the Number of Self-Generating LSAs for an OSPF Process

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    router ospf process-id

    4.    router-id ip-address

    5.    log -adjacency-changes [detail]

    6.    max-lsa maximum-number [threshold-percentage] [warning-only] [ignore-time minutes] [ignore-count count-number] [reset-time minutes]

    7.    network ip-address wildcard-mask area area-id

    8.    end

    9.    show ip ospf [process-id area-id] database[database-summary]


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 router ospf process-id


    Example:
    Router(config)# router ospf 1
     

    Enables OSPF routing.

    • The process-id argument identifies the OSPF process.
     
    Step 4 router-id ip-address


    Example:
    Router(config-router)# router-id 10.0.0.1
     

    Specifies a fixed router ID for an OSPF process.

     
    Step 5 log -adjacency-changes [detail]


    Example:
    Router(config-router)# log-adjacency-changes
     

    Configures the router to send a syslog message when an OSPF neighbor goes up or down.

     
    Step 6 max-lsa maximum-number [threshold-percentage] [warning-only] [ignore-time minutes] [ignore-count count-number] [reset-time minutes]


    Example:
    Router(config-router)# max-lsa 12000
     

    Limits the number of nonself-generated LSAs that an OSPF routing process can keep in the OSPF link-state database (LSDB).

     
    Step 7 network ip-address wildcard-mask area area-id


    Example:
    Router(config-router)# network 209.165.201.1 255.255.255.255 area 0
     

    Defines the interfaces on which OSPF runs and defines the area ID for those interfaces.

     
    Step 8 end


    Example:
    Router(config-router)# end
     

    Ends the current configuration mode and returns to Privileged EXEC mode.

     
    Step 9 show ip ospf [process-id area-id] database[database-summary]


    Example:
    Router# show ip ospf 2000 database database-summary
     

    Displays lists of information related to the OSPF database for a specific router.

    • Use this command to verify the number of nonself-generated LSAs on a router.
     

    Example

    The show ip ospf command is entered with the database-summary keyword to verify the actual number of nonself-generated LSAs on a router. This command can be used at any time to display lists of information related to the OSPF database for a specific router.

    Router# show ip ospf 2000 database database-summary
     
                 OSPF Router with ID (192.168.1.3) (Process ID 2000)
    Area 0 database summary
      LSA Type      Count    Delete   Maxage
      Router        5        0        0       
      Network       2        0        0       
      Summary Net   8        2        2       
      Summary ASBR  0        0        0       
      Type-7 Ext    0        0        0       
        Prefixes redistributed in Type-7  0
      Opaque Link   0        0        0       
      Opaque Area   0        0        0       
      Subtotal      15       2        2       
    Process 2000 database summary
      LSA Type      Count    Delete   Maxage
      Router        5        0        0       
      Network       2        0        0       
      Summary Net   8        2        2       
      Summary ASBR  0        0        0       
      Type-7 Ext    0        0        0       
      Opaque Link   0        0        0       
      Opaque Area   0        0        0       
      Type-5 Ext    4        0        0       
        Prefixes redistributed in Type-5  0
      Opaque AS     0        0        0       
      Non-self      16      
      Total         19       2        2 
    

    Configuration Examples for OSPF Link-State Database Overload Protection

    Setting a Limit for LSA Generation Example

    In the following example, the router is configured to not accept any more nonself-generated LSAs once a maximum of 14,000 has been exceeded:

    Router(config)# router ospf 1
    Router(config-router)# router-id 192.168.0.1
    Router(config-router)# log-adjacency-changes
    Router(config-router)# max-lsa 14000
    Router(config-router)# area 33 nssa
    Router(config-router)# network 192.168.0.1 0.0.0.0 area 1
    Router(config-router)# network 192.168.5.1 0.0.0.0 area 1
    Router(config-router)# network 192.168.2.1 0.0.0.0 area 0
    

    In the following example, the show ip ospf command has been entered to confirm the configuration:

    Router# show ip ospf 1
    Routing Process "ospf 1" with ID 192.168.0.1
    Supports only single TOS(TOS0) routes
    Supports opaque LSA
    Supports Link-local Signaling (LLS)
    Supports area transit capability
    Maximum number of non self-generated LSA allowed 14000
       Threshold for warning message 75%
       Ignore-time 5 minutes, reset-time 10 minutes
       Ignore-count allowed 5, current ignore-count 0
    It is an area border and autonomous system boundary router
    

    In the following example, the following output appears when the show ip ospf command has been entered during the time when the router is in the ignore state:

    Router# show ip ospf 1
    Routing Process "ospf 1" with ID 192.168.0.1
    Supports only single TOS(TOS0) routes
    Supports opaque LSA
    Supports Link-local Signaling (LLS)
    Supports area transit capability
    Maximum number of non self-generated LSA allowed 14000
       Threshold for warning message 75%
       Ignore-time 5 minutes, reset-time 10 minutes
       Ignore-count allowed 5, current ignore-count 1
       Ignoring all neighbors due to max-lsa limit, time remaining: 00:04:52
    It is an area border and autonomous system boundary router
    

    The following output appears when the show ip ospf command has been entered after the router left the ignore state:

    Router# show ip ospf 1
    Routing Process "ospf 1" with ID 192.168.0.1
    Supports only single TOS(TOS0) routes
    Supports opaque LSA
    Supports Link-local Signaling (LLS)
    Supports area transit capability
    Maximum number of non self-generated LSA allowed 14000
       Threshold for warning message 75%
       Ignore-time 5 minutes, reset-time 10 minutes
       Ignore-count allowed 5, current ignore-count 1 - time remaining: 00:09:51
    It is an area border and autonomous system boundary router
    

    The following output appears when the show ip ospf command has been entered for a router that is permanently in the ignore state:

    Router# show ip ospf 1
    Routing Process "ospf 1" with ID 192.168.0.1
    Supports only single TOS(TOS0) routes
    Supports opaque LSA
    Supports Link-local Signaling (LLS)
    Supports area transit capability
    Maximum number of non self-generated LSA allowed 14000
       Threshold for warning message 75%
       Ignore-time 5 minutes, reset-time 10 minutes
       Ignore-count allowed 5, current ignore-count 6
       Permanently ignoring all neighbors due to max-lsa limit
    It is an area border and autonomous system boundary router

    Additional References

    The following sections provide references related to the OSPF Link-State Database Overload Protection feature.

    Related Documents

    Related Topic

    Document Title

    Configuring OSPF

    " Configuring OSPF"

    OSPF commands

    Cisco IOS IP Routing: OSPF Command Reference

    Cisco IOS master command list, all releases

    Cisco IOS Master Command List, All Releases

    Standards

    Standard

    Title

    None

    --

    MIBs

    MIB

    MIBs Link

    No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

    To locate and download MIBs for selected platforms, Cisco IOS XE releases, and feature sets, use Cisco MIB Locator found at the following URL:

    http:/​/​www.cisco.com/​go/​mibs

    RFCs

    RFC

    Title

    None

    --

    Technical Assistance

    Description

    Link

    The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

    http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

    Feature Information for OSPF Link-State Database Overload Protection

    The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

    Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

    Table 1 Feature Information for OSPF Link-State Database Overload Protection

    Feature Name

    Releases

    Feature Information

    OSPF Link-State Database Overload Protection

    Cisco IOS XE Release 2.1

    The OSPF Link-State Database Overload Protection feature allows you to limit the number of nonself-generated link-state advertisements (LSAs) for a given OSPF process. Excessive LSAs generated by other routers in the OSPF domain can substantially drain the CPU and memory resources of the router.

    The following commands are introduced or modified in the feature documented in this module:

    • max-lsa