IPv6 First-Hop Security Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000)
IPv6 Snooping
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IPv6 Snooping

Contents

IPv6 Snooping

The IPv6 Snooping feature bundles several Layer 2 IPv6 first-hop security features, including IPv6 neighbor discovery inspection, IPv6 device tracking, IPv6 address glean, and IPv6 binding table recovery, to provide security and scalability. IPv6 ND inspection operates at Layer 2, or between Layer 2 and Layer 3, to provide IPv6 functions with security and scalability.

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.

Restrictions for IPv6 Snooping

The IPv6 snooping feature is not supported on Etherchannel ports.

Information About IPv6 Snooping

IPv6 Snooping

The IPv6 Snooping feature bundles several Layer 2 IPv6 first-hop security features, including IPv6 Address Glean and IPv6 Device Tracking. The feature operates at Layer 2, or between Layer 2 and Layer 3, and provides IPv6 features with security and scalability. This feature mitigates some of the inherent vulnerabilities for the neighbor discovery mechanism, such as attacks on duplicate address detection (DAD), address resolution, device discovery, and the neighbor cache.

IPv6 Snooping learns and secures bindings for stateless autoconfiguration addresses in Layer 2 neighbor tables and analyzes ND messages in order to build a trusted binding table. IPv6 ND messages that do not have valid bindings are dropped. An ND message is considered trustworthy if its IPv6-to-MAC mapping is verifiable.

When IPv6 Snooping is configured on a target (which varies depending on platform target support and may include device ports, switch ports, Layer 2 interfaces, Layer 3 interfaces, and VLANs), capture instructions are downloaded to the hardware to redirect the ND protocol and Dynamic Host Configuration Protocol (DHCP) for IPv6 traffic up to the switch integrated security features (SISF) infrastructure in the routing device. For ND traffic, messages such as NS, NA, RS, RA, and REDIRECT are directed to SISF. For DHCP, UDP messages sourced from port 546 or 547 are redirected.

IPv6 Snooping registers its "capture rules" to the classifier, which aggregates all rules from all features on a given target and installs the corresponding ACL down into the platform-dependent modules. Upon receiving redirected traffic, the classifier calls all entry points from any registered feature (for the target on which the traffic is being received), including the IPv6 snooping entry point. This entry point is the last to be called, so any decision (such as drop) made by another feature supersedes the IPv6 Snooping decision.

IPv6 Device Tracking

IPv6 device tracking provides IPv6 host liveness tracking so that a neighbor table can be immediately updated when an IPv6 host disappears.

IPv6 First-Hop Security Binding Table

The IPv6 First-Hop Security Binding Table recovery mechanism feature enables the binding table to recover in the event of a device reboot. A database table of IPv6 neighbors connected to the device is created from information sources such as ND snooping. This database, or binding, table is used by various IPv6 guard features to validate the link-layer address (LLA), the IPv4 or IPv6 address, and prefix binding of the neighbors to prevent spoofing and redirect attacks.

This mechanism enables the binding table to recover in the event of a device reboot. The recovery mechanism will block any data traffic sourced from an unknown source; that is, a source not already specified in the binding table and previously learned through ND or DHCP gleaning. This feature recovers the missing binding table entries when the resolution for a destination address fails in the destination guard. When a failure occurs, a binding table entry is recovered by querying the DHCP server or the destination host, depending on the configuration.

Recovery Protocols and Prefix Lists

The IPv6 First-Hop Security Binding Table Recovery Mechanism feature introduces the capability to provide a prefix list that is matched before the recovery is attempted for both DHCP and NDP.

If an address does not match the prefix list associated with the protocol, then the recovery of the binding table entry will not be attempted with that protocol. The prefix list should correspond to the prefixes that are valid for address assignment in the Layer 2 domain using the protocol. The default is that there is no prefix list, in which case the recovery is attempted for all addresses. The command to associate a prefix list to a protocol is protocol {dhcp | ndp} [prefix-list prefix-list-name].

IPv6 Device Tracking

IPv6 device tracking provides IPv6 host liveness tracking so that a neighbor table can be immediately updated when an IPv6 host disappears.

IPv6 Address Glean

IPv6 address glean is the foundation for many other IPv6 features that depend on an accurate binding table. It inspects ND and DHCP messages on a link to glean addresses, and then populates the binding table with these addresses. This feature also enforces address ownership and limits the number of addresses any given node is allowed to claim.

The following figure shows how IPv6 address glean works.

Figure 1. IPv6 Address Glean

How to Configure IPv6 Snooping

Configuring IPv6 Snooping on an Interface

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    ipv6 snooping policy snooping-policy

    4.    exit

    5.    interface type number

    6.    ipv6 snooping attach-policy snooping-policy


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 snooping policy snooping-policy


    Example:
    Device(config)# ipv6 snooping policy policy1
     

    Configures an IPv6 snooping policy and enters IPv6 snooping configuration mode.

     
    Step 4 exit


    Example:
    Device(config-ipv6-snooping)# exit
     

    Exits IPv6 snooping configuration mode.

     
    Step 5 interface type number


    Example:
    Device(config)# interface Gigabitethernet 0/0/1
     

    Enters interface configuration mode.

     
    Step 6 ipv6 snooping attach-policy snooping-policy


    Example:
    Device(config-if)# ipv6 snooping attach-policy policy1
     

    Attaches the IPv6 snooping policy to the interface.

     

    Verifying and Troubleshooting IPv6 ND Inspection

    SUMMARY STEPS

      1.    enable

      2.    show ipv6 snooping capture-policy [interface type number]

      3.    show ipv6 snooping counter [interface type number]

      4.    show ipv6 snooping features

      5.    show ipv6 snooping policies [interface type number]

      6.    debug ipv6 snooping


    DETAILED STEPS
        Command or Action Purpose
      Step 1 enable


      Example:
      Device> enable 
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 show ipv6 snooping capture-policy [interface type number]


      Example:
      Device# show ipv6 snooping capture-policy interface ethernet 0/0 
       

      Displays snooping ND message capture policies.

       
      Step 3 show ipv6 snooping counter [interface type number]


      Example:
      Device# show ipv6 snooping counter interface FastEthernet 4/12 
       

      Displays information about the packets counted by the interface counter.

       
      Step 4 show ipv6 snooping features


      Example:
      Device# show ipv6 snooping features 
       

      Displays information about snooping features configured on the device.

       
      Step 5 show ipv6 snooping policies [interface type number]


      Example:
      Device# show ipv6 snooping policies
       

      Displays information about the configured policies and the interfaces to which they are attached.

       
      Step 6 debug ipv6 snooping


      Example:
      Device# debug ipv6 snooping
       

      Enables debugging for snooping information in IPv6.

       

      Configuring IPv6 Device Tracking

      Configuring IPv6 First-Hop Security Binding Table Content

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    ipv6 neighbor binding {ipv6-address | ipv6-prefix} interface type number [hardware-address | mac-address][tracking [disable | enable | retry-interval value] | reachable-lifetime value]

        4.    ipv6 neighbor binding max-entries entries

        5.    ipv6 neighbor binding logging

        6.    exit

        7.    show ipv6 neighbor binding


      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 neighbor binding {ipv6-address | ipv6-prefix} interface type number [hardware-address | mac-address][tracking [disable | enable | retry-interval value] | reachable-lifetime value]


        Example:
        Device(config)# ipv6 neighbor binding 2001:DB8:0:ABCD::1 interface GigabitEthernet 0/0/1 reachable-lifetime 100
         

        Adds a static entry to the binding table database.

         
        Step 4 ipv6 neighbor binding max-entries entries


        Example:
        Device(config)# ipv6 neighbor binding max-entries 100
         

        Specifies the maximum number of entries that are allowed to be inserted in the binding table cache.

         
        Step 5 ipv6 neighbor binding logging


        Example:
        Device(config)# ipv6 neighbor binding logging
         

        Enables the logging of binding table main events.

         
        Step 6 exit


        Example:
        Device(config)# exit
         

        Exits global configuration mode and enters privileged EXEC mode.

         
        Step 7 show ipv6 neighbor binding


        Example:
        Device# show ipv6 neighbor binding
         

        Displays the contents of a binding table.

         

        Configuring the IPv6 First-Hop Security Binding Table Recovery Mechanism

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    ipv6 neighbor binding ipv6-address interface type number

          4.    ipv6 prefix-list list-name permit ipv6-prefix/prefix-length ge ge-value

          5.    ipv6 snooping policy snooping-policy-id

          6.    destination-glean {recovery | log-only} [dhcp]

          7.    data-glean {recovery | log-only} [ndp | dhcp]

          8.    prefix-glean

          9.    protocol dhcp [prefix-list prefix-list-name]

          10.    exit

          11.    ipv6 destination-guard policy policy-name

          12.    enforcement {always | stressed}

          13.    exit

          14.    interface type number

          15.    ipv6 snooping attach-policy snooping-policy

          16.    ipv6 destination-guard attach-policy policy-name

          17.    end


        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 neighbor binding ipv6-address interface type number


          Example:
          Device(config)# ipv6 neighbor binding 2001:db8::1 interface Gigabitethernet3/0/1
          
           

          Adds a static entry to the binding table database.

           
          Step 4 ipv6 prefix-list list-name permit ipv6-prefix/prefix-length ge ge-value


          Example:
          Device(config)# ipv6 prefix-list abc permit 2001:DB8::/64 ge 128
          
           

          Creates an entry in an IPv6 prefix list.

           
          Step 5 ipv6 snooping policy snooping-policy-id


          Example:
          Device(config)# ipv6 snooping policy xyz
          
           

          Enters IPv6 snooping configuration mode and allows you to modify the configuration of the snooping policy specified.

           
          Step 6 destination-glean {recovery | log-only} [dhcp]


          Example:
          Device(config-ipv6-snooping)# destination-glean recovery dhcp
          
           

          Specifies that destination addresses should be recovered from DHCP.

          Note   

          If logging (without recovery) is required, use the destination-glean log-only command.

           
          Step 7 data-glean {recovery | log-only} [ndp | dhcp]


          Example:
          Device(config-ipv6-snooping)# data-glean recovery ndp
          
           

          Enables IPv6 first-hop security binding table recovery using source (or “data”) address gleaning.

          Note   

          If logging (without recovery) is required, use the data-glean log-only command.

           
          Step 8 prefix-glean


          Example:
          Device(config-ipv6-snooping)# prefix-glean 
          
           

          Enables the device to glean prefixes from IPv6 router advertisements (RAs) or Dynamic Host Configuration protocol (DHCP)

           
          Step 9 protocol dhcp [prefix-list prefix-list-name]


          Example:
          Device(config-ipv6-snooping)# protocol dhcp prefix-list abc
          
           

          (Optional) Specifies that addresses should be gleaned with DHCP and associates the protocol with a specific IPv6 prefix list.

           
          Step 10 exit


          Example:
          Device(config-ipv6-snooping)# exit
          
           

          Exits IPv6 snooping configuration mode and returns to global configuration mode.

           
          Step 11 ipv6 destination-guard policy policy-name


          Example:
          Device(config)# ipv6 destination-guard policy xyz
          
           

          (Optional) Enters destination guard configuration mode and allows you to modify the configuration of the specified destination guard policy.

           
          Step 12 enforcement {always | stressed}


          Example:
          Device(config-destguard)# enforcement stressed
          
           

          Sets the enforcement level of the policy to be either enforced under all conditions or only when the system is under stress.

           
          Step 13 exit


          Example:
          Device(config-destguard)# exit
          
           

          Exits destination guard configuration mode and returns to global configuration mode.

           
          Step 14 interface type number


          Example:
          Device(config)# interface Gigabitethernet 0/0/1
           

          Enters interface configuration mode.

           
          Step 15 ipv6 snooping attach-policy snooping-policy


          Example:
          Device(config-if)# ipv6 snooping attach-policy xyz
           

          Attaches the IPv6 snooping policy to the interface.

           
          Step 16 ipv6 destination-guard attach-policy policy-name


          Example:
          Device(config-if)# ipv6 destination-guard attach-policy xyz
          
           
          Attaches the destination guard policy to the specified interface.
          Note   

          For information about how to configure an IPv6 destination guard policy, see the “IPv6 Destination Guard” module.

           
          Step 17 end


          Example:
          Device(config-if)# end
          
           

          Exits interface configuration mode and returns to privileged EXEC mode.

           

          Configuring Address Gleaning and Associating Recovery Protocols with Prefix Lists

          SUMMARY STEPS

            1.    enable

            2.    configure terminal

            3.    ipv6 snooping policy snooping-policy-id

            4.    protocol {dhcp | ndp} [prefix-list prefix-list-name]

            5.    end


          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 snooping policy snooping-policy-id


            Example:
            Device(config)# ipv6 snooping policy 200
            
             

            Enters IPv6 snooping configuration mode and allows you to modify the configuration of the snooping policy specified.

             
            Step 4 protocol {dhcp | ndp} [prefix-list prefix-list-name]


            Example:
            Device(config-ipv6-snooping)# protocol dhcp prefix-list dhcp_prefix_list
            
             

            Specifies that address should be gleaned with dynamic Host Configuration Protocol (DHCP) and associates a recovery protocol (DHCP) with the prefix list.

             
            Step 5 end


            Example:
            Device(config-ipv6-snooping)# end
            
             

            Exits IPv6 snooping configuration mode and returns to privileged EXEC mode.

             

            Configuring IPv6 Device Tracking

            Perform this task to provide fine tuning for the life cycle of an entry in the binding table for the IPv6 Device Tracking feature. For IPv6 device tracking to work, the binding table needs to be populated.

            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    ipv6 neighbor tracking [retry-interval value]


            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 neighbor tracking [retry-interval value]


              Example:
              Device(config)# ipv6 neighbor tracking
               

              Tracks entries in the binding table.

               

              Configuring IPv6 Prefix Glean

              SUMMARY STEPS

                1.    enable

                2.    configure terminal

                3.    ipv6 snooping policy snooping-policy

                4.    prefix-glean [only]


              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 snooping policy snooping-policy


                Example:
                Device(config)# ipv6 snooping policy policy1
                 

                Configures an IPv6 snooping policy and enters IPv6 snooping policy configuration mode.

                 
                Step 4 prefix-glean [only]


                Example:
                Device(config-ipv6-snooping)# prefix-glean
                 

                Enables the device to glean prefixes from IPv6 RAs or DHCPv6 traffic.

                 

                Configuration Examples for IPv6 Snooping

                Example: Configuring IPv6 ND Inspection on an Interface

                Device(config)# ipv6 snooping policy policy1
                Device(config-ipv6-snooping)# exit
                Device(config)# interface Gigabitethernet 0/0/1
                Device(config-if)# ipv6 snooping attach-policy policy1
                . 
                .
                .
                Device# show ipv6 snooping policies interface gigabitethernet 0/0/1
                Target               Type  Policy               Feature        Target range
                Gi0/0/1              PORT  my_policy            Destination Gu vlan all
                Gi0/0/1              PORT  policy1              Snooping       vlan all
                

                Example: Configuring IPv6 Binding Table Content

                Device(config)# ipv6 neighbor binding 2001:DB8:0:ABCD::1 interface GigabitEthernet 0/0/1 reachable-lifetime 100
                Device(config)# ipv6 neighbor binding max-entries 100
                Device(config)# ipv6 neighbor binding logging
                Device(config)# exit
                

                Example: Configuring IPv6 First-Hop Security Binding Table Recovery

                Device> enable
                Device# configure terminal
                Device(config)# ipv6 neighbor binding 2001:db8::1 interface Gigabitethernet3/0/1
                Device(config)# ipv6 prefix-list abc permit 2001:DB8::/64 ge 128
                Device(config)# ipv6 snooping policy xyz
                Device(config-ipv6-snooping)# destination-glean recovery dhcp
                Device(config-ipv6-snooping)# data-glean recovery ndp
                Device(config-ipv6-snooping)# prefix-glean
                Device(config-ipv6-snooping)# protocol dhcp prefix-list abc
                Device(config-ipv6-snooping)# exit
                Device(config)# ipv6 destination-guard policy xyz
                Device(config-destguard)# enforcement stressed
                Device(config-destguard)# exit
                Device(config)# interface Gigabitethernet 0/0/1
                Device(config-if)# ipv6 snooping attach-policy xyz
                Device(config-if)# ipv6 destination-guard attach-policy xyz
                Device(config-if)# end

                Example: Configuring Address Gleaning and Associating Recovery Protocols with Prefix Lists

                The following example shows that NDP will be used for the recovery for all addresses and that DHCP will be used to recover addresses that match the prefix list called dhcp_prefix_list:

                Device(config-ipv6-snooping)# protocol ndp 
                Device(config-ipv6-snooping)# protocol dhcp prefix-list dhcp_prefix_list
                

                Additional References for IPv6 Source Guard and Prefix Guard

                Related Documents

                Related Topic

                Document Title

                IPv6 addressing and connectivity

                IPv6 Configuration Guide

                IPv4 addressing

                IP Addressing: IPv4 Addressing Configuration Guide

                Cisco IOS commands

                Cisco IOS Master Command 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

                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 Snooping

                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 Snooping

                Feature Name

                Releases

                Feature Information

                IPv6 Snooping

                12.2(50)SY

                15.0(1)SY

                15.0(2)SE

                15.1(2)SG

                15.3(1)S

                Cisco IOS XE Release 3.2SE

                Cisco IOS XE Release 3.8S

                Cisco IOS XE Release 3.9S

                IPv6 snooping bundles several Layer 2 IPv6 first-hop security features, including IPv6 ND inspection, IPv6 device tracking, IPv6 address glean, and IPv6 first-hop security binding table recovery, to provide security and scalability. IPv6 snooping operates at Layer 2, or between Layer 2 and Layer 3, to provide IPv6 functions with security and scalability.

                In Cisco IOS XE Release 3.9S, support was added for the Cisco CSR 1000V and the Cisco ASR 1000 Series Routers.

                The following commands were introduced or modified: data-glean, debug ipv6 snooping, destination-glean, device-role, drop-unsecure, ipv6 nd inspection, ipv6 nd inspection policy, ipv6 neighbor binding logging, ipv6 neighbor binding max-entries, ipv6 neighbor binding vlan, ipv6 neighbor tracking, ipv6 snooping attach-policy, ipv6 snooping policy, prefix-glean, protocol (IPv6), sec-level minimum, show ipv6 neighbor binding, show ipv6 snooping capture-policy, show ipv6 snooping counters, show ipv6 snooping features, show ipv6 snooping policies, tracking, trusted-port.