IPv6 Anycast Address

An IPv6 anycast address is an address that is assigned to a set of interfaces that typically belong to different nodes. Anycast addresses are syntactically indistinguishable from unicast addresses, because anycast addresses are allocated from the unicast address space.

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.

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.

Information About IPv6 Anycast Address

IPv6 Address Type: Anycast

An anycast address is an address that is assigned to a set of interfaces that typically belong to different nodes. A packet sent to an anycast address is delivered to the closest interface (as defined by the routing protocols in use) identified by the anycast address. Anycast addresses are syntactically indistinguishable from unicast addresses, because anycast addresses are allocated from the unicast address space. Assigning a unicast address to more than one interface makes a unicast address an anycast address. Nodes to which the anycast address is assigned must be explicitly configured to recognize that the address is an anycast address.


Note

Anycast addresses can be used only by a , not a host, and anycast addresses must not be used as the source address of an IPv6 packet.

The figure below shows the format of the subnet anycast address; the address has a prefix concatenated by a series of zeros (the interface ID). The subnet anycast address can be used to reach a device on the link that is identified by the prefix in the subnet anycast address.

Figure 1. Subnet Anycast Address Format

How to Configure IPv6 Anycast Address

Configuring IPv6 Anycast Addressing

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. interface type number
  4. ipv6 address ipv6-prefix/prefix-length anycast

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 tunnel0

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

Step 4

ipv6 address ipv6-prefix/prefix-length anycast

Example:


Device(config-if)# ipv6 address 2002:db8:c058::/128 anycast

Specifying the ipv6 address anycast command adds an IPv6 anycast address.

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 Anycast Address

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 Anycast Address

Feature Name

Releases

Feature Information

IPv6: Anycast Address

12.2(25)SEA

12.2(25)SG

12.2(33)SRA

12.2(33)SXH

12.3(4)T

15.0(2)SG

Cisco IOS XE Release 2.1

3.2.0SG

An anycast address is an address that is assigned to a set of interfaces that typically belong to different nodes. Anycast addresses are syntactically indistinguishable from unicast addresses, because anycast addresses are allocated from the unicast address space.

The following commands were introduced or modified: ipv6 address anycast , show ipv6 interface .