First Hop Redundancy Protocols Configuration Guide, Cisco IOS Release 15M&T
HSRP for IPv6
HSRP for IPv6
Last Updated: December 4, 2012
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.
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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Prerequisites for HSRP for IPv6
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 routers 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)
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
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 router solicitation (RS) 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. RS 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 autoconfigure without needing to wait for the next scheduled RA message.
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 Device 1 and Device 2. The show standby command is issued for each device to verify its 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)
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.
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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
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