IP Mobility: Mobile IP Configuration Guide, Cisco IOS Release 15M&T
Mobile IPv6 Home Agent
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Mobile IPv6 Home Agent

Mobile IPv6 Home Agent

Mobile IP is part of both IPv4 and IPv6 standards. Mobile IP allows a host device to be identified by a single IP address even though the device may move its physical point of attachment from one network to another. Regardless of movement between different networks, connectivity at the different points is achieved seamlessly without user intervention. Roaming from a wired network to a wireless or wide-area network is also done with ease. Mobile IP provides ubiquitous connectivity for users, whether they are within their enterprise networks or away from home.

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.

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Information About Mobile IPv6 Home Agent

Mobile IPv6 Overview

Mobile IPv4 provides an IPv4 node with the ability to retain the same IPv4 address and maintain uninterrupted network and application connectivity while traveling across networks. In Mobile IPv6, the IPv6 address space enables Mobile IP deployment in any kind of large environment. No foreign agent is needed to use Mobile IPv6.

System infrastructures do not need an upgrade to accept Mobile IPv6 nodes. IPv6 autoconfiguration simplifies mobile node (MN) Care of Address (CoA) assignment.

Mobile IPv6 benefits from the IPv6 protocol itself; for example, Mobile IPv6 uses IPv6 option headers (routing, destination, and mobility) and benefits from the use of neighbor discovery.

Mobile IPv6 provides optimized routing, which helps avoid triangular routing. Mobile IPv6 nodes work transparently even with nodes that do not support mobility (although these nodes do not have route optimization).

Mobile IPv6 is fully backward-compatible with existing IPv6 specifications. Therefore, any existing host that does not understand the new mobile messages will send an error message, and communications with the mobile node will be able to continue, albeit without the direct routing optimization.

How Mobile IPv6 Works

To implement Mobile IPv6, you need a home agent on the home subnet on which the mobile node’s home address resides. The IPv6 home address (HA) is assigned to the mobile node. The mobile node obtains a new IPv6 address (the CoA) on networks to which it connects. The home agent accepts BUs from the mobile node informing the agent of the mobile node’s location. The home agent then acts as proxy for the mobile node, intercepting traffic to the mobile node’s home address and tunneling it to the mobile node.

The mobile node informs a home agent on its original home network about its new address, and the correspondent node communicates with the mobile node about the CoA. Because of the use of ingress filtering, the mobile node reverses tunnel return traffic to the home agent, so that the mobile node source address (that is, its home address) will always be topographically correct.

Mobile IPv6 is the ability of a mobile node to bypass the home agent when sending IP packets to a correspondent node. Optional extensions make direct routing possible in Mobile IPv6, though the extensions might not be implemented in all deployments of Mobile IPv6.

Direct routing is built into Mobile IPv6, and the direct routing function uses the IPv6 routing header and the IPv6 destination options header. The routing header is used for sending packets to the mobile node using its current CoA, and the new home address destination option is used to include the mobile node’s home address, because the current CoA is the source address of the packet.

Mobile IPv6 Home Agent

The home agent is one of three key components in Mobile IPv6. The home agent works with the correspondent node and mobile node to enable Mobile IPv6 functionality:

  • Home agent--The home agent maintains an association between the mobile mode’s home IPv4 or IPv6 address and its CoA (loaned address) on the foreign network.

  • Correspondent node--The correspondent node is the destination IPv4 or IPv6 host in session with a mobile node.

  • Mobile node--An IPv4 or IPv6 host that maintains network connectivity using its home IPv4 or IPv6 address, regardless of the link (or network) to which it is connected.

The following sections describe Mobile IPv6 home agent functionality:

Binding Cache in Mobile IPv6 Home Agent

A separate binding cache is maintained by each IPv6 node for each of its IPv6 addresses. When the router sends a packet, it searches the binding cache for an IPv6 address before it searches the neighbor discovery conceptual destination cache.

The binding cache for any one of a node’s IPv6 addresses may contain one entry for each mobile node home address. The contents of all of a node’s binding cache entries are cleared when it reboots.

Binding cache entries are marked either as home registration or correspondent registration entries. A home registration entry is deleted when its binding lifetime expires; other entries may be replaced at any time through a local cache replacement policy.

Binding Update List in Mobile IPv6 Home Agent

A binding update (BU) list is maintained by each mobile node. The BU list records information for each BU sent by this mobile node whose lifetime has not yet expired. The BU list includes all BUs sent by the mobile node--those bindings sent to correspondent nodes, and those bindings sent to the mobile node’s home agent.

The mobility extension header has a new routing header type and a new destination option, and it is used during the BU process. This header is used by mobile nodes, correspondent nodes, and home agents in all messaging related to the creation and management of bindings.

Home Agents List

A home agents list is maintained by each home agent and each mobile node. The home agents list records information about each home agent from which this node has recently received a router advertisement in which the home agent (H) bit is set.

Each home agent maintains a separate home agents list for each link on which it is serving as a home agent. This list is used by a home agent in the dynamic home agent address discovery mechanism. Each roaming mobile node also maintains a home agents list that enables it to notify a home agent on its previous link when it moves to a new link.

IPv6 Neighbor Discovery with Mobile IPv6

The IPv6 neighbor discovery feature has the following modifications to allow the feature to work with Mobile IPv6:

  • Modified router advertisement message format--has a single flag bit that indicates home agent service

  • Modified prefix information option format--allows a router to advertise its global address

  • New advertisement interval option format

  • New home agent information option format

  • Changes to sending router advertisements

  • Provide timely movement detection for mobile nodes

How to Configure Mobile IPv6 Home Agent

Enabling Mobile IPv6 on the Router

You can customize interface configuration parameters before you start Mobile IPv6 (see the Customizing Mobile IPv6 on the Interface) or while Mobile IPv6 is in operation.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    interface type number

    4.    ipv6 mobile home-agent [preference preference-value

    5.    exit

    6.    exit

    7.    show ipv6 mobile globals

    8.    show ipv6 mobile home-agent interface-type interface-number [prefix]]


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 interface type number


    Example:
    Router(config)# interface Ethernet 2
     

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

     
    Step 4 ipv6 mobile home-agent [preference preference-value


    Example:
    Router(config-if)# ipv6 mobile home-agent
     

    Initializes and starts the Mobile IPv6 home agent on a specific interface.

     
    Step 5 exit


    Example:
    Router(config-if)# exit
     

    Exits interface configuration mode, and returns the router to global configuration mode.

     
    Step 6 exit


    Example:
    Router(config)# exit
     

    Exits global configuration mode, and returns the router to privileged EXEC mode.

     
    Step 7 show ipv6 mobile globals


    Example:
    Router# show ipv6 mobile globals
     

    Displays global Mobile IPv6 parameters.

     
    Step 8 show ipv6 mobile home-agent interface-type interface-number [prefix]]


    Example:
    Router# show ipv6 mobile home-agent
     

    Displays local and discovered neighboring home agents.

     

    Configuring Binding Information for Mobile IPv6

    Before you start Mobile IPv6 on a specified interface, you can configure binding information on the router.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    ipv6 mobile home-agent

      4.    binding access access-list-name | auth-option | seconds | maximum | refresh

      5.    exit

      6.    exit

      7.    show ipv6 mobile binding [care-of-address address | home-address address | interface-type interface-number

      8.    show ipv6 mobile traffic


    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 ipv6 mobile home-agent


      Example:
      Router(config)# ipv6 mobile home-agent
       

      Places the router in home-agent configuration mode.

       
      Step 4 binding access access-list-name | auth-option | seconds | maximum | refresh


      Example:
      Router(config-ha)# binding
       

      Configures binding options for the Mobile IPv6 home agent feature.

       
      Step 5 exit


      Example:
      Router(config-ha)# exit
       

      Exits home-agent configuration mode, and returns the router to global configuration mode.

       
      Step 6 exit


      Example:
      Router(config)# exit
       

      Exits global configuration mode, and returns the router to privileged EXEC mode.

       
      Step 7 show ipv6 mobile binding [care-of-address address | home-address address | interface-type interface-number


      Example:
      Router# show ipv6 mobile binding
       

      Displays information about the binding cache.

       
      Step 8 show ipv6 mobile traffic


      Example:
      Router# show ipv6 mobile traffic
       

      Displays information about BUs received and BAs sent.

       

      Customizing Mobile IPv6 on the Interface

      Perform this task to customize interface configuration parameters for your router configuration. You can set these interface configuration parameters before you start Mobile IPv6 or while Mobile IPv6 is in operation. You can customize any of these parameters, as desired.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    interface type number

        4.    ipv6 mobile home-agent [preference preference-value

        5.    ipv6 nd advertisement-interval

        6.    ipv6 nd prefix {ipv6-prefix / prefix-length | default} [[valid-lifetime preferred-lifetime | at valid-date preferred-date] | infinite | no-advertise | off-link | no-rtr-address | no-autoconfig

        7.    ipv6 nd ra interval {maximum-secs [minimum-secs] | msec maximum-msecs [minimum-msecs]}


      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 interface type number


        Example:
        Router(config)# interface serial 3
         

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

         
        Step 4 ipv6 mobile home-agent [preference preference-value


        Example:
        Router(config-if)# ipv6 mobile home-agent preference 10
         

        Configures the Mobile IPv6 home agent preference value on the interface.

         
        Step 5 ipv6 nd advertisement-interval


        Example:
        Router(config-if)# ipv6 nd advertisement-interval
         

        Configures the advertisement interval option to be sent in RAs.

         
        Step 6 ipv6 nd prefix {ipv6-prefix / prefix-length | default} [[valid-lifetime preferred-lifetime | at valid-date preferred-date] | infinite | no-advertise | off-link | no-rtr-address | no-autoconfig


        Example:
        Router(config-if)# ipv6 nd prefix 2001:DB8::/35 1000 900
         

        Configures which IPv6 prefixes are included in IPv6 RAs.

         
        Step 7 ipv6 nd ra interval {maximum-secs [minimum-secs] | msec maximum-msecs [minimum-msecs]}


        Example:
        Router(config-if)# ipv6 nd ra interval 201
         

        Configures the interval between IPv6 RA transmissions on an interface.

         

        Configuration Examples for Mobile IPv6 Home Agent

        Example Enabling Mobile IPv6 on the Router

        The following example shows how to configure and enable Mobile IPv6 on a specified interface:

        Router> enable
        Router# config terminal
        Router(config)# interface Ethernet 1
        Router(config-if)# ipv6 mobile home-agent

        Example: Viewing IPv6 Mobile Information on an Interface

        Device(config-if)# ipv6 nd ra-interval 100 60
        Subsequent use of the show ipv6 interface then displays the interval as follows: 
        
        Router(config)# show ipv6 interface ethernet 1/0 
        Ethernet1/0 is administratively down, line protocol is down 
          IPv6 is enabled, link-local address is FE80::A8BB:CCFF:FE00:5A01 [TEN]
          No Virtual link-local address(es):
          No global unicast address is configured
          Joined group address(es):
            FF02::1
            FF02::2
          MTU is 1500 bytes
          ICMP error messages limited to one every 100 milliseconds
          ICMP redirects are enabled
          ICMP unreachables are sent
          ND DAD is enabled, number of DAD attempts: 1
          ND reachable time is 30000 milliseconds
          ND advertised reachable time is 0 milliseconds
          ND advertised retransmit interval is 0 milliseconds
          ND router advertisements are sent every 60 to 100 seconds
          ND router advertisements live for 1800 seconds
          ND advertised default router preference is Medium
          Hosts use stateless autoconfig for addresses.
        

        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

        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 Mobile IPv6 Home Agent

        Table 1 Feature Information for Mobile IPv6 Home Agent

        Feature Name

        Releases

        Feature Information

        Mobile IPv6 Home Agent

        12.3(4)T

        The Mobile IPv6 feature uses the IPv6 address space to enable Mobile IP deployment in any kind of large environment. No foreign agent is needed to use Mobile IPv6.

        The following commands were introduced or modified: binding access, ipv6 mobile home-agent, ipv6 nd advertisement-interval, ipv6 nd prefix, ipv6 nd ra interval, show ipv6 mobile globals, show ipv6 mobile home-agent.