HSRP for IPv6

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.

Prerequisites for HSRP for IPv6

HSRP version 2 must be enabled on an interface before HSRP for IPv6 can be configured.

Information About HSRP for IPv6

HSRP for IPv6 Overview

The HSRP is an FHRP designed to allow for transparent failover of the first-hop IP device. HSRP provides high network availability by providing first-hop routing redundancy for IP hosts on Ethernet configured with a default gateway IP address. HSRP is used in a group of devices for selecting an active device and a standby device. In a group of device interfaces, the active device is the device of choice for routing packets; the standby device is the device that takes over when the active device fails or when preset conditions are met.

IPv6 hosts learn of available IPv6 devices through IPv6 neighbor discovery RA messages. These are multicast periodically, or may be solicited by hosts. HSRP is designed to provide only a virtual first hop for IPv6 hosts.

An HSRP IPv6 group has a virtual MAC address that is derived from the HSRP group number, and a virtual IPv6 link-local address that is, by default, derived from the HSRP virtual MAC address. Periodic RAs are sent for the HSRP virtual IPv6 link-local address when the HSRP group is active. These RAs stop after a final RA is sent when the group leaves the active state.

Periodic RAs for the interface link-local address stop after a final RA is sent while at least one virtual IPv6 link-local address is configured on the interface. No restrictions occur for the interface IPv6 link-local address other than that mentioned for the RAs. Other protocols continue to receive and send packets to this address.

HSRP uses a priority mechanism to determine which HSRP configured device is to be the default active device. To configure a device as the active device, you assign it a priority that is higher than the priority of all the other HSRP-configured devices. The default priority is 100, so if you configure just one device to have a higher priority, that device will be the default active device.

HSRP IPv6 Virtual MAC Address Range

HSRP IPv6 uses a different virtual MAC address block than does HSRP for IP:

0005.73A0.0000 through 0005.73A0.0FFF (4096 addresses)

HSRP IPv6 UDP Port Number

Port number 2029 has been assigned to HSRP IPv6.

How to Enable HSRP for IPv6

Enabling an HSRP Group for IPv6 Operation

HSRP version 2 must be enabled on an interface before HSRP IPv6 can be configured.

Enabling HSRP Version 2

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. interface type number
  4. standby version {1 | 2}

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 0/0/0

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

Step 4

standby version {1 | 2}

Example:

Device(config-if)# standby version 2

Changes the version of the HSRP.

  • Version 1 is the default.

Enabling and Verifying an HSRP Group for IPv6 Operation

In this task, when you enter the standby ipv6 command, a link-local address is generated from the link-local prefix, and 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.

A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format. Link-local addresses are used in the stateless autoconfiguration process. Nodes on a local link can use link-local addresses to communicate; the nodes do not need site-local or globally unique addresses to communicate.

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 router 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 detection 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. Router solicitation messages, which have a value of 133 in the Type field of the ICMP packet header, are sent by hosts at system startup so that the host can immediately autoconfigure 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 {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 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 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 GigabitEthernet 0/0/0

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

Step 5

standby [group-number ] ipv6 {link-local-address | autoconfig }

Example:

Device(config-if)# standby 1 ipv6 autoconfig

Activates the HSRP in IPv6.

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 the device 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 GigabitEthernet 0/0/0

Displays the usability status of interfaces configured for IPv6.

Configuration Examples for HSRP for IPv6

Example: Configuration and Verification for an HSRP Group

The following example shows configuration and verification for an HSRP group for IPv6 that consists of Device1 and Device2. The show standby command is issued for each device to verify the device's configuration:

Device 1 configuration 

interface FastEthernet0/0.100
description DATA VLAN for PCs 
encapsulation dot1Q 100 
ipv6 address 2001:DB8:CAFE:2100::BAD1:1010/64 
standby version 2 
standby 101 priority 120 
standby 101 preempt delay minimum 30 
standby 101 authentication ese 
standby 101 track Serial0/1/0.17 90 
standby 201 ipv6 autoconfig 
standby 201 priority 120 
standby 201 preempt delay minimum 30 
standby 201 authentication ese 
standby 201 track Serial0/1/0.17 90 
Device1# show standby
FastEthernet0/0.100 - Group 101 (version 2) 
State is Active 
2 state changes, last state change 5w5d 
Active virtual MAC address is 0000.0c9f.f065 
Local virtual MAC address is 0000.0c9f.f065 (v2 default) 
Hello time 3 sec, hold time 10 sec 
Next hello sent in 2.296 secs 
Authentication text "ese"
Preemption enabled, delay min 30 secs 
Active router is local 
Priority 120 (configured 120)
Track interface Serial0/1/0.17 state Up decrement 90 
IP redundancy name is "hsrp-Fa0/0.100-101" (default) 
FastEthernet0/0.100 - Group 201 (version 2) 
State is Active 
2 state changes, last state change 5w5d 
Virtual IP address is FE80::5:73FF:FEA0:C9 
Active virtual MAC address is 0005.73a0.00c9 
Local virtual MAC address is 0005.73a0.00c9 (v2 IPv6 default) 
Hello time 3 sec, hold time 10 sec 
Next hello sent in 2.428 secs 
Authentication text "ese" 
Preemption enabled, delay min 30 secs 
Active router is local 
Standby router is FE80::20F:8FFF:FE37:3B70, priority 100 (expires in 7.856 sec) 
Priority 120 (configured 120) 
Track interface Serial0/1/0.17 state Up decrement 90 
IP redundancy name is "hsrp-Fa0/0.100-201" (default)

Device 2 configuration 

interface FastEthernet0/0.100
description DATA VLAN for Computers 
encapsulation dot1Q 100
ipv6 address 2001:DB8:CAFE:2100::BAD1:1020/64 
standby version 2 
standby 101 preempt 
standby 101 authentication ese 
standby 201 ipv6 autoconfig 
standby 201 preempt 
standby 201 authentication ese
Device2# show standby
FastEthernet0/0.100 - Group 101 (version 2) 
State is Standby 
7 state changes, last state change 5w5d 
Active virtual MAC address is 0000.0c9f.f065 
Local virtual MAC address is 0000.0c9f.f065 (v2 default) 
Hello time 3 sec, hold time 10 sec 
Next hello sent in 0.936 secs 
Authentication text "ese" 
Preemption enabled 
MAC address is 0012.7fc6.8f0c 
Standby router is local 
Priority 100 (default 100) 
IP redundancy name is "hsrp-Fa0/0.100-101" (default) 
FastEthernet0/0.100 - Group 201 (version 2) 
State is Standby 
7 state changes, last state change 5w5d
Virtual IP address is FE80::5:73FF:FEA0:C9
Active virtual MAC address is 0005.73a0.00c9 
Local virtual MAC address is 0005.73a0.00c9 (v2 IPv6 default)
Hello time 3 sec, hold time 10 sec
Next hello sent in 0.936 secs 
Authentication text "ese" 
Preemption enabled 
Active router is FE80::212:7FFF:FEC6:8F0C, priority 120 (expires in 7.548 sec) 
MAC address is 0012.7fc6.8f0c 
Standby router is local 
Priority 100 (default 100) 
IP redundancy name is "hsrp-Fa0/0.100-201" (default)

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

VRRP commands

Cisco IOS IP Application Services Command Reference

Object tracking

Configuring Enhanced Object Tracking

Hot Standby Routing Protocol (HSRP)

Configuring HSRP

In Service Software Upgrace (ISSU)

"In Service Software Upgrade Process" in the High Availability Configuration Guide

Gateway Load Balancing Protocol (GLBP)

Configuring GLBP

Stateful Switchover

The Stateful Switchover section in theHigh Availability Configuration Guide

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

MIBs

MIBs

MIBs Link

VRRP MIB

To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

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

RFCs

RFCs

Title

RFC 2338

Virtual Router Redundancy Protocol

RFC 2787

Definitions of Managed Objects for the Virtual Router Redundancy Protocol

RFC 3768

Virtual Router Redundancy Protocol (VRRP)

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 HSRP for IPv6

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.

Glossary

  • CPE --Customer premises equipment

  • FHRP --First hop redundancy protocol

  • GLBP --Gateway load balancing protocol

  • HSRP --Hot standby routing protocol

  • NA --Neighbor advertisement

  • ND --Neighbor Discovery

  • NS --Neighbor solicitation

  • PE --Provider equipment

  • RA --Router advertisement

  • RS --Router solicitation