HSRP: Global IPv6 Address

IPv6 routing protocols ensure device-to-device resilience and failover. However, in situations in which the path between a host and the first-hop device fails, or the first-hop device itself fails, first hop redundancy protocols (FHRPs) ensure host-to-device resilience and failover.

The Hot Standby Router Protocol (HSRP) protects data traffic in case of a gateway failure.


Note
A note on link local addresses

The HSRP protocol uses a link local address as part of the protocol and this is not changed by the global address feature. Consider the global address feature as exchanging global addresses within the protocol for use, but the protocol itself still uses link locals for its protocol operation. If you only configure a global address, then there is a link-local address that is automatically allocated using the Extended Unique Identifier (EUI-64) method. You can use the show standby command to see the allocated link local address. You can still configure an IPv6 link local address by manual configuration if you require it. Manual configuration takes the group out of the 'implicit link-local' mode and replaces the automatic link local address with the configured one. If the configured one is later removed, but there is still a global address, then another implicit link local address is recalculated and applied.

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Information About HSRP Global IPv6 Address

HSRP: Global IPv6 Address

The HSRP global IPv6 address feature allows users to configure multiple nonlink local addresses as virtual addresses, and it allows for the storage and management of multiple global IPv6 virtual addresses in addition to the existing primary link-local address. If an IPv6 address is used, it must include an IPv6 prefix length. If a link-local address is used, it must not have a prefix.

The figure below depicts a deployment scenario that uses an HSRP IPv6 global virtual interface:

In the figure above, the provider equipment (PE) devices need to inject a route to reach the customer premises equipment (CPE) from the backbone devices. Because there are two CPEs, HSRP is convenient to use. The static route will be set with a link-local next hop (FE80::1:1:1:CAFE). If this address is injected in the backbone, this route is useless with a link-local next hop, as link-local addresses only have scope within the Layer 2 local LAN space. To address this issue, the next hop of the static route toward the virtual address must be set to a non link-local address, so backbone devices can route packets to the PE devices. At the next-hop address resolution, the active HSRP group member will reply to neighbor solicitation (NS) messages sent to the non link-local address.

Jitter timers

Jitter timers are used in HSRP. They are recommended for timers running on services that work realtime and scale. Jitter timers are intended to significantly improve the reliability of HSRP, and other FHRP protocols, by reducing the chance of bunching of HSRP groups operations, and thus help reduce CPU and network traffic spikes. In the case of HSRP, a given device may have up to 4000 operational groups configured. In order to distribute the load on the device and network, the HSRP timers use a jitter. A given timer instance may take up to 20% more than the configured value. For example, for a hold time set to 15 seconds, the actual hold time may take 18 seconds.

In HSRP, the Hello timer (which sends the Hello Packet) has a negative Jitter, while the Holddown timer (which checks for failure of a peer) has a positive jitter.

How to Enable HSRP Global IPv6 Address

Enabling and Verifying an HSRP Group for IPv6 Operation

In this task, when you enter the standby ipv6 command, a modified EUI-64 format interface identifier is generated in which the EUI-64 interface identifier is created from the relevant HSRP virtual MAC address

In IPv6, a device on the link advertises in RA messages any site-local and global prefixes, and its willingness to function as a default device for the link. RA messages are sent periodically and in response to device solicitation messages, which are sent by hosts at system startup

A node on the link can automatically configure site-local and global IPv6 addresses by appending its interface identifier (64 bits) to the prefixes (64 bits) included in the RA messages. The resulting 128-bit IPv6 addresses configured by the node are then subjected to duplicate address detec tion to ensure their uniqueness on the link. If the prefixes advertised in the RA messages are globally unique, then the IPv6 addresses configured by the node are also guaranteed to be globally unique. Device solicitation messages, which have a value of 133 in the Type field of the ICMPv6 packet header, are sent by hosts at system startup so that the host can immediately auto-configure without needing to wait for the next scheduled RA message.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    ipv6 unicast-routing

    4.    interface type number

    5.    standby [group-number] ipv6 {ipv6-global-address | ipv6-address/prefix-length | ipv6-prefix/prefix-length | link-local-address | autoconfig}

    6.    standby [group-number] preempt [delay minimum seconds | reload seconds | sync seconds]

    7.    standby [group-number] priority priority

    8.    exit

    9.    show standby [type number [group]] [all | brief]

    10.    show ipv6 interface [brief] [interface-type interface-number] [prefix]


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 ipv6 unicast-routing


    Example: 
    Device(config)# ipv6 unicast-routing
     

    Enables the forwarding of IPv6 unicast datagrams.

    • The ipv6 unicast-routing command must be enabled for HSRP for IPv6 to work.

     
    Step 4 interface type number


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

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

     
    Step 5 standby [group-number] ipv6 {ipv6-global-address | ipv6-address/prefix-length | ipv6-prefix/prefix-length | link-local-address | autoconfig}


    Example: 
    Device(config-if)# standby 1 ipv6 autoconfig
     

    Activates the HSRP in IPv6.

    If an IPv6 address is used, it must include an IPv6 prefix length. If a link-local address is used, it must not have a prefix.

     
    Step 6 standby [group-number] preempt [delay minimum seconds | reload seconds | sync seconds]


    Example: 
    Device(config-if)# standby 1 preempt
     

    Configures HSRP preemption and preemption delay.

     
    Step 7 standby [group-number] priority priority


    Example: 
    Device(config-if)# standby 1 priority 110
     

    Configures HSRP priority.

     
    Step 8 exit


    Example: 
    Device(config-if)# exit
     

    Returns to privileged EXEC mode.

     
    Step 9 show standby [type number [group]] [all | brief]


    Example: 
    Device# show standby
     

    Displays HSRP information.

     
    Step 10 show ipv6 interface [brief] [interface-type interface-number] [prefix]


    Example: 
    Device# show ipv6 interface ethernet 0/0
     

    Displays the usability status of interfaces configured for IPv6.

     

    Configuration Example for HSRP Global IPv6 Address

    Example: Configuring HSRP Global IPv6 Addresses

    This example shows three HSRP global IPv6 addresses with an explicitly configured link-local address: 

    Device(config)# interface ethernet 0/0
Device(config-if)# no ip address 
Device(config-if)# ipv6 address 2001::DB8:1/64
Device(config-if)# standby 1 ipv6 FE80::1:CAFE
Device(config-if)# standby 1 ipv6 2001::DB8:2/64
Device(config-if)# standby 1 ipv6 2001:DB8::3/64
Device(config-if)# standby 1 ipv6 2001:DB8::4/64
Device(config-if)# exit

    Additional References for HSRP Global IPv6 Address

    Related Documents

    Related Topic

    Document Title

    Cisco IOS commands

    Cisco IOS Master Command List, All Releases

    HSRP commands

    Cisco IOS First Hop Redundancy Protocols Command Reference

    Troubleshooting HSRP

    Hot Standby Router Protocol: Frequently Asked Questions

    IPv6 addressing and connectivity

    IPv6 Configuration Guide

    IPv6 commands

    Cisco IOS IPv6 Command Reference

    Cisco IOS IPv6 features

    Cisco IOS IPv6 Feature Mapping

    RFCs

    RFCs

    Title

    RFCs for IPv6

    IPv6 RFCs

    Technical Assistance

    Description

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    Feature Information for HSRP: Global IPv6 Address

    Table 1 Feature Information for HSRP: Global IPv6 Address

    Feature Name

    Releases

    Feature Information

    HSRP: Global IPv6 Address

    Cisco IOS XE 3.6E

    The HSRP global IPv6 address feature allows users to configure multiple non-link local addresses as virtual addresses.

    In Cisco IOS Release Cisco IOS XE Release 3.6E, this feature is supported on the following platforms:

    • Cisco Catalyst 3850 Series Switches

    • Cisco Catalyst 3650 Series Switches

    • Cisco Catalyst 4500E Supervisor Engine 7L-E

    • Cisco Catalyst 4500-X Series Switches

    • Cisco Catalyst 4500E Supervisor Engine 8-E

    The following commands were introduced or modified: standby ipv6.