IPv6 Neighbor Discovery Cache

The IPv6 neighbor discovery cache feature allows static entries to be made in the IPv6 neighbor cache.

The per-interface neighbor discovery cache limit function can be used to prevent any particular customer attached to an interface from overloading the neighbor discovery cache, whether intentionally or unintentionally.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see 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 document.

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.

Information About IPv6 Static Cache Entry for Neighbor Discovery

IPv6 Neighbor Discovery

The IPv6 neighbor discovery process uses ICMP messages and solicited-node multicast addresses to determine the link-layer address of a neighbor on the same network (local link), verify the reachability of a neighbor, and track neighboring devices.

The IPv6 static cache entry for neighbor discovery feature allows static entries to be made in the IPv6 neighbor cache. Static routing requires an administrator to manually enter IPv6 addresses, subnet masks, gateways, and corresponding Media Access Control (MAC) addresses for each interface of each device into a table. Static routing enables more control but requires more work to maintain the table. The table must be updated each time routes are added or changed.

Per-Interface Neighbor Discovery Cache Limit

The number of entries in the Neighbor Discovery cache can be limited by interface. Once the limit is reached, no new entries are allowed. The per-interface Neighbor Discovery cache limit function can be used to prevent any particular customer attached to an interface from overloading the Neighbor Discovery cache, whether intentionally or unintentionally.

When this feature is enabled globally, a common per-interface cache size limit is configured on all interfaces on the device. When this feature is enabled per interface, a cache size limit is configured on the associated interface. The per-interface limit overrides any globally configured limit.

How to Configure IPv6 Neighbor Discovery Cache

Configuring a Neighbor Discovery Cache Limit on a Specified Interface

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    interface type number

    4.    ipv6 nd cache interface-limit size [log rate]


DETAILED STEPS
      Command or Action Purpose
    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 GigabitEthernet 1/0/0
     

    Specifies an interface type and number, and places the device in interface configuration mode.

     
    Step 4 ipv6 nd cache interface-limit size [log rate]


    Example: 
    Device(config-if)# ipv6 nd cache interface-limit 1
     

    Configures a Neighbor Discovery cache limit on a specified interface on the device.

    • Issuing this command overrides any configuration that may have been created by issuing the ipv6 nd cache interface-limit in global configuration mode.
     

    Configuring a Neighbor Discovery Cache Limit on All Device Interfaces

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    ipv6 nd cache interface-limit size [log rate]


    DETAILED STEPS
        Command or Action Purpose
      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 ipv6 nd cache interface-limit size [log rate]


      Example: 
      Device(config)# ipv6 nd cache interface-limit 4
       

      Configures a neighbor discovery cache limit on all interfaces on the device.

       

      Configuration Examples for IPv6 Neighbor Discovery Cache

      Example: Configuring a Neighbor Discovery Cache Limit

      Device# show ipv6 interface GigabitEthernet2/0/0

Interface GigabitEthernet2/0/0, entries 2, static 0, limit 4 

IPv6 Address               Age Link-layer Addr State  Interface
2001:0db8::94               	 0 aabb.cc00.5d02    REACH  GE2/0/0
FE80::A8BB:CCFF:FE00:5D02  0 aabb.cc00.5d02    DELAY  GE2/0/0

      Additional References

      Related Documents

      Related Topic

      Document Title

      IPv6 addressing and connectivity

      IPv6 Configuration Guide

      Cisco IOS commands

      Cisco IOS Master Commands List, All Releases

      IPv6 commands

      Cisco IOS IPv6 Command Reference

      Cisco IOS IPv6 features

      Cisco IOS IPv6 Feature Mapping

      Standards and RFCs

      Standard/RFC

      Title

      RFCs for IPv6

      IPv6 RFCs

      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 releases, and feature sets, use Cisco MIB Locator found at the following URL:

      http:/​/​www.cisco.com/​go/​mibs

      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 IPv6 Neighbor Discovery Cache

      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 IPv6 Neighbor Discovery Cache

      Feature Name

      Releases

      Feature Information

      IPv6: Per-Interface Neighbor Discovery Cache Limit

      15.1(1)SY

      15.1(3)T

      Cisco IOS XE Release 2.6

      The per-interface neighbor discovery cache limit function can be used to prevent any particular customer attached to an interface from overloading the neighbor discovery cache, whether intentionally or unintentionally.

      The following commands were introduced or modified: ipv6 nd cache interface-limit, show ipv6 interface.

      IPv6 Static Cache Entry for Neighbor Discovery

      12.2(8)T

      12.2(17)SX1

      12.2(25)SEA

      12.2(25)SG

      12.2(33)SRA

      15.3(1)S

      Cisco IOS XE Release 2.1

      15.0(2)SG

      3.2.0SG

      The IPv6 static cache entry for Neighbor Discovery feature allows static entries to be made in the IPv6 neighbor cache.

      The following commands were introduced or modified: ipv6 nd cache interface-limit, show ipv6 interface.