IP Routing: OSPF Configuration Guide, Cisco IOS XE Release 3S
Prefix Suppression Support for OSPFv3
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Prefix Suppression Support for OSPFv3

Contents

Prefix Suppression Support for OSPFv3

This feature enables Open Shortest Path First version 3 (OSPFv3) to hide the IPv4 and IPv6 prefixes of connected networks from link-state advertisements (LSAs). When OSPFv3 is deployed in large networks, limiting the number of IPv4 and IPv6 prefixes that are carried in the OSPFv3 LSAs can speed up OSPFv3 convergence.

This feature can also be utilized to enhance the security of an OSPFv3 network by allowing the network administrator to prevent IP routing toward internal nodes.

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 Prefix Suppression Support for OSPFv3

Before you can use the mechanism to exclude IPv4 and IPv6 prefixes from LSAs, the OSPFv3 routing protocol must be configured.

Information About Prefix Suppression Support for OSPFv3

OSPFv3 Prefix Suppression Support

The OSPFv3 Prefix Suppression Support feature allows you to hide IPv4 and IPv6 prefixes that are configured on interfaces running OSPFv3.

In OSPFv3, addressing semantics have been removed from the OSPF protocol packets and the main LSA types, leaving a network-protocol-independent core. This means that Router-LSAs and network-LSAs no longer contain network addresses, but simply express topology information. The process of hiding prefixes is simpler in OSPFv3 and suppressed prefixes are simply removed from the intra-area-prefix-LSA. Prefixes are also propagated in OSPFv3 via link LSAs

The OSPFv3 Prefix Suppression feature provides a number of benefits.The exclusion of certain prefixes from adverstisements means that there is more memory available for LSA storage, bandwidth and buffers for LSA flooding, and CPU cycles for origination and flooding of LSAs and for SPF computation. Prefixes are also filtered from link LSAs. A device only filters locally configured prefixes, not prefixes learnt via link LSAs. In addition, security has been improved by reducing the possiblity of remote attack with the hiding of transit-only networks.

Globally Suppress IPv4 and IPv6 Prefix Advertisements by Configuring the OSPFv3 Process

You can reduce OSPFv3 convergence time by configuring the OSPFv3 process on a device to prevent the advertisement of all IPv4 and IPv6 prefixes by using the prefix-suppression command in router configuration mode or address-family configuration mode.


Note


Prefixes that are associated with loopbacks, secondary IP addresses, and passive interfaces are not suppressed by the router mode or the address-family configuration commands because typical network designs require prefixes to remain reachable.


Suppress IPv4 and IPv6 Prefix Advertisements on a Per-Interface Basis

You can explicitly configure an OSPFv3 interface not to advertise its IP network to its neighbors by using the ipv6 ospf prefix-suppression command or the ospfv3 prefix-suppression command in interface configuration mode.


Note


If you have globally suppressed IPv4 and IPv6 prefixes from connected IP networks by configuring the prefix-suppression router configuration command, the interface configuration command takes precedence over the router configuration command.


How to Configure Prefix Suppression Support for OSPFv3

Configuring Prefix Suppression Support of the OSPFv3 Process

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    router ospfv3 process-id [vrf vpn-name]

    4.    prefix-suppression

    5.    end

    6.    show ospfv3


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 router ospfv3 process-id [vrf vpn-name]


    Example:
    Device(config)# router ospfv3 23
     

    Configures an OSPFv3 routing process and enters router configuration mode.

     
    Step 4 prefix-suppression


    Example:
    Device(config-router)# prefix-suppression
     

    Prevents OSPFv3 from advertising all IPv4 and IPv6 prefixes, except prefixes that are associated with loopbacks, secondary IP addresses, and passive interfaces.

     
    Step 5 end


    Example:
    Device(config-router)# end
     

    Returns to privileged EXEC mode.

     
    Step 6 show ospfv3


    Example:
    Device# show ospfv3
     

    Displays general information about OSPFv3 routing processes.

    Note   

    Use this command to verify that IPv4 and IPv6 prefix suppression has been enabled.

     

    Configuring Prefix Suppression Support of the OSPFv3 Process in Address-Family Configuration Mode

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    router ospfv3 process-id [vrf vpn-name]

      4.    address-family ipv6 unicast

      5.    prefix-suppression

      6.    end

      7.    show ospfv3


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 configure terminal


      Example:
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3 router ospfv3 process-id [vrf vpn-name]


      Example:
      Device(config)# router ospfv3 23
       

      Configures an OSPFv3 routing process and enters router configuration mode.

       
      Step 4 address-family ipv6 unicast


      Example:
      Device(config-router)# address-family ipv6 unicast
       

      Enters IPv6 address family configuration mode for OSPFv3.

       
      Step 5 prefix-suppression


      Example:
      Device(config-router-af)# prefix-suppression
       

      Prevents OSPFv3 from advertising all IPv4 and IPv6 prefixes, except prefixes that are associated with loopbacks, secondary IP addresses, and passive interfaces.

       
      Step 6 end


      Example:
      Device(config-router-af)# end
       

      Returns to privileged EXEC mode.

       
      Step 7 show ospfv3


      Example:
      Device# show ospfv3
       

      Displays general information about OSPFv3 routing processes.

      Note   

      Use this command to verify that IPv4 and IPv6 prefix suppression has been enabled.

       

      Configuring Prefix Suppression Support on a Per-Interface Basis

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    interface type number

        4.    Do one of the following:

        • ipv6 ospf prefix-suppression [disable]
        • ospfv3 prefix-suppression disable

        5.    end

        6.    show ospfv3 interface


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Device> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.

         
        Step 2 configure terminal


        Example:
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3 interface type number


        Example:
        Device(config)# interface serial 0/0
         

        Configures an interface type and enters interface configuration mode.

         
        Step 4Do one of the following:
        • ipv6 ospf prefix-suppression [disable]
        • ospfv3 prefix-suppression disable


        Example:
        Device(config-if)# ipv6 ospf prefix-suppression


        Example:
        Device(config-if)# ospfv3 1 prefix-suppression disable
         

        Prevents OSPFv3 from advertising IPv4 and IPv6 prefixes that belong to a specific interface, except those that are associated with secondary IP addresses.

        • When you enter the ipv6 ospf prefix-suppression command or the ospfv3 prefix-suppression command in interface configuration mode, it takes precedence over the prefix-suppression command that is entered in router configuration mode.

         
        Step 5 end


        Example:
        Device(config-if)# end
         

        Returns to privileged EXEC mode.

         
        Step 6 show ospfv3 interface


        Example:
        Device# show ospfv3 interface
         

        Displays OSPFv3-related interface information.

        Note   

        Use this command to verify that IPv4 and IPv6 prefix suppression has been enabled for a specific interface.

         

        Troubleshooting IPv4 and IPv6 Prefix Suppression

        SUMMARY STEPS

          1.    enable

          2.    debug ospfv3 lsa-generation

          3.    debug condition interface interface-type interface-number [dlci dlci] [vc {vci | vpi | vci}]

          4.    show debugging

          5.    show logging [slot slot-number | summary]


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Device> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.

           
          Step 2 debug ospfv3 lsa-generation


          Example:
          Device# debug ospfv3 lsa-generation
           

          Displays informations about each OSPFv3 LSA that is generated.

           
          Step 3 debug condition interface interface-type interface-number [dlci dlci] [vc {vci | vpi | vci}]


          Example:
          Device# debug condition interface serial 0/0
           

          Limits output for some debug commands on the basis of the interface or virtual circuit.

           
          Step 4 show debugging


          Example:
          Device# show debugging
           

          Displays information about the types of debugging that are enabled for your device.

           
          Step 5 show logging [slot slot-number | summary]


          Example:
          Device# show logging
           

          Displays the state of syslog and the contents of the standard system logging buffer.

           

          Configuration Examples for Prefix Suppression Support for OSPFv3

          Example: Configuring Prefix Suppression Support for OSPFv3

          The following example shows how to configure prefix suppression support for OSPFv3 in router configuration mode:

          router ospfv3 1
           prefix-suppression
           !
           address-family ipv6 unicast
            router-id 0.0.0.6
            exit-address-family
          

          The following example shows how to configure prefix suppression support for OSPFv3 in address-family configuration mode:

          router ospfv3 1
           !
           address-family ipv6 unicast
            router-id 10.0.0.6
            prefix-suppression
            exit-address-family 
          

          The following example shows how to configure prefix suppression support for OSPFv3 in interface configuration mode:

          interface Ethernet0/0
           ip address 10.0.0.1 255.255.255.0
           ipv6 address 2001:201::201/64
           ipv6 enable
           ospfv3 prefix-suppression
           ospfv3 1 ipv4 area 0
           ospfv3 1 ipv6 area 0
           end
          

          Additional References for Prefix Suppression Support for OSPFv3

          Related Documents

          Related Topic

          Document Title

          Configuring OSPF

          “Configuring OSPF”

          OSPF commands

          Cisco IOS IP Routing: OSPF Command Reference

          Cisco IOS commands

          Cisco IOS Master Command List, All Releases

          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 Prefix Suppression Support for OSPFv3

          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 Prefix Suppression Support for OSPFv3

          Feature Name

          Releases

          Feature Information

          Prefix Suppression Support for OSPFv3

          Cisco IOS XE Release 3.8S

          This feature enables Open Shortest Path First version 3 (OSPFv3) to hide the IPv4 and IPv6 prefixes of connected networks from link-state advertisements (LSAs).

          This feature can also be used to enhance the security of an OSPFv3 network by allowing the network administrator to prevent IP routing toward internal nodes.

          The following commands were introduced or modified:

          • ipv6 ospf prefix-suppression

          • ospfv3 prefix-suppression

          • prefix-suppression (OSPFv3)