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This document provides configuration tasks for the Cisco implementation of IP version 6 (IPv6) in the Cisco IOS software and includes the following sections:
IPv6 features are supported only in the 12.0 ST, 12.0 S, and 12.2 T Cisco IOS software release trains, starting at Cisco IOS Release 12.0(21)ST, 12.0(22)S, and 12.2(2)T, respectively. The 12.0 ST Cisco IOS software release train was merged with the 12.0 S Cisco IOS software release train starting at Cisco IOS Release 12.0(22)S; therefore, subsequent releases of only the 12.0 S and 12.2 T Cisco IOS software release trains support additional IPv6 features. This document, along with the following IPv6 for Cisco IOS Software feature documentation is updated with information about additional IPv6 features at each subsequent release of the applicable Cisco IOS software release trains:
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Note The Start Here: Cisco IOS Software Release Specifics for IPv6 Features document details which IPv6 features are supported in each release of the 12.0 ST, 12.0 S, and 12.2 T Cisco IOS software trains. Not all IPv6 features may be supported in your Cisco IOS software release. We strongly recommend that you read the entire Start Here: Cisco IOS Software Release Specifics for IPv6 Features document before reading the other IPv6 for Cisco IOS Software feature documentation. |
The other IPv6 for Cisco IOS Software feature documentation provides IPv6 overview, configuration, and command reference information for IPv6 features in each release of the 12.0 ST, 12.0 S, and 12.2 T Cisco IOS software trains.
By default, IPv6 routing is disabled in the Cisco IOS software. To enable IPv6 routing, you must first enable the forwarding of IPv6 traffic globally on the router and then you must assign IPv6 addresses to individual interfaces in the router.
The tasks described in the following sections explain how to enable IPv6 routing on a Cisco router. Each task in the list is identified as either required or optional:
See the "IPv6 Routing and IPv6 Address Configuration Example" section for a configuration example.
To enable the forwarding of IPv6 traffic globally on the router, use the following command in global configuration mode:
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An IPv6 address must be configured on an interface for the interface to forward IPv6 traffic. Configuring a site-local or global IPv6 address on an interface automatically configures a link-local address and activates IPv6 for that interface. Additionally, the configured interface automatically joins the following required multicast groups for that link:
To configure an IPv6 address on an interface, use the following commands beginning in global configuration mode:
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Note The ipv6-address argument in the ipv6 address command must be in the form documented in RFC 2373
where the address is specified in hexadecimal using 16-bit values between colons. The ipv6-prefix argument in the ipv6 address command must be in the form documented in RFC 2373 where the address is specified in hexadecimal using 16-bit values between colons. The /prefix-length argument in the ipv6 address command is a decimal value that indicates how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address) A slash mark must precede the decimal value. |
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Note In Cisco IOS Release 12.2(4)T or later releases, Cisco IOS Release 12.0(21)ST, and Cisco IOS
Release 12.0(22)S or later releases, the ipv6 address or ipv6 address eui-64 command can be used to
configure multiple IPv6 global and site-local addresses within the same prefix on an interface. Multiple
IPv6 link-local addresses on an interface are not supported. Prior to Cisco IOS Releases 12.2(4)T, 12.0(21)ST, and 12.0(22)S, the Cisco IOS command-line interface (CLI) displays the following error message when multiple IPv6 addresses within the same prefix on an interface are configured: Prefix <prefix-number> already assigned to <interface-type> See the "IPv6 Routing and IPv6 Address Configuration Example"section for a configuration example of multiple IPv6 global and site-local addresses within the same prefix on an interface. |
To verify that IPv6 processing of packets is enabled globally on the router and on applicable interfaces, and that an IPv6 address is configured on applicable interfaces, enter the show running-config EXEC command:
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Note Display text was omitted from the example. |
To verify that IPv6 addresses are configured correctly, enter the show ipv6 interface EXEC command. The following example shows the IPv6 addresses configured for Ethernet interface 0:
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Note For a description of each output display field, refer to the show ipv6 interface command in the IPv6 for Cisco IOS Software, File 3 of 3: Commands document. |
In the following example, IPv6 is enabled on the router with both a link-local address and a global address based on the IPv6 prefix 3ffe:c00:c18:1::/64. The EUI-64 interface ID is used in the low-order 64 bits of both addresses. Output from the show ipv6 interface EXEC command is included to show how the interface ID (260:3EFF:FE47:1530) is appended to the link-local prefix FE80::/64 of Ethernet interface 0.
In the following example, multiple IPv6 global addresses within the prefix 3000::/64 are configured on Ethernet interface 0:
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Note All site-local addresses must be within the same site. |
This section describes how to configure Cisco Express Forwarding (CEF) for IPv6 (CEFv6) and distributed CEF for IPv6 (dCEFv6). For a complete description of the CEFv6 and dCEFv6 commands that appear in this section, refer to the IPv6 for Cisco IOS Software, File 3 of 3: Commands document. For a complete description of the CEF for IPv4 (CEFv4) and distributed CEF for IPv4 (dCEFv4) commands available in the Cisco IOS software, refer to the Release 12.2 Cisco IOS Switching Services Command Reference publication. To locate documentation for all other IPv4 commands, use the command reference master index or search online.
dCEFv6 and CEFv6 function the same and offer the same benefits as CEFv4 and dCEFv4. In Cisco IOS Release 12.0(22)S or later releases, IPv6 enhancements to CEFv6 and dCEFv6 include support for separate FIBs for IPv6 global, site-local, and link-local addresses. Prior to Cisco IOS Releases 12.0(22)S—in Cisco IOS Release 12.0(21)ST—IPv6 enhancements to dCEFv6 consisted of support for IPv6 addresses and prefixes.
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Note CEFv6 and dCEFv6 switching of IPv6 link-local addresses is planned for a later release of the Cisco IOS software; therefore, in Cisco IOS Release 12.0(22)S, IPv6 router interfaces do not use the IPv6 link-local FIB. |
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Note The following sections describe the configuration tasks for enabling CEFv6 and dCEFv6, and for configuring CEFv6 network accounting. The following sections do not provide in-depth information on customizing CEFv6 because CEF switching functions the same in IPv6 as it does in IPv4. Refer to the "Configuring Cisco Express Forwarding" chapter of the Release 12.2 Cisco IOS Switching Services Configuration Guide publication for information on customizing CEF switching. Wherever applicable, the "Usage Guidelines" section of each command page in the IPv6 for Cisco IOS Software, File 3 of 3: Commands document lists the equivalent CEFv4 command for each new CEFv6 command. Refer to the "Configuring Cisco Express Forwarding" chapter of the Release 12.2 Cisco IOS Switching Services Configuration Guide publication as you customize your CEFv6 configuration. |
The tasks in the following sections explain how to configure CEFv6 and dCEFv6. Each task in the list is identified as either required or optional:
See the "IPv6 Routing and IPv6 Address Configuration Example" section for a configuration example.
To enable CEFv6 globally on a nondistributed architecture platform, such as the Cisco 7200 series routers, or a distributed architecture platform, such as the Cisco 7500 series routers, use the following command in global configuration mode:
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Note Some distributed architecture platforms, such as the Cisco 7500 series routers, support both CEFv6 and
dCEFv6. When CEFv6 is configured on distributed platforms, CEF switching is performed by the Route
Processor (RP). By default, the Cisco 12000 series Internet routers, a distributed architecture platform,
support only dCEFv6 (CEF switching is performed by the line cards). In the 12.2 T Cisco IOS software release train, IPv6 supports only process switching for packet forwarding. Support for CEFv6 and dCEFv6 by the Cisco 7200 series routers and Cisco 7500 series routers is planned for a later release of the 12.2 T Cisco IOS software release train. |
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Note To forward CEFv6 traffic, the forwarding of IPv6 unicast datagrams must be configured globally on the router by using the ipv6 unicast-routing global configuration command, and an IPv6 address and IPv6 processing must be configured on an interface by using the ipv6 address interface configuration command. |
To enable dCEFv6 globally on a distributed architecture platform, such as the Cisco 7500 series routers, use the following command in global configuration mode:
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Note When dCEFv6 is configured on distributed platforms, CEF switching is performed by the line cards. dCEFv6 is enabled by default on the Cisco 12000 series Internet routers and disabled by default on the Cisco 7500 series routers. |
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Note To forward dCEFv6 traffic, the forwarding of IPv6 unicast datagrams must be configured globally on the router by using the ipv6 unicast-routing global configuration command, and an IPv6 address and IPv6 processing must be configured on an interface by using the ipv6 address interface configuration command. |
Network accounting for CEFv6 and dCEFv6 enables you to better understand CEFv6 traffic patterns within your network by collecting statistics specific to CEFv6 and dCEFv6 traffic. For example, network accounting for CEFv6 and dCEFv6 enables you to collect information such as the number of packets and bytes switched to a destination or the number of packets switched through a destination.
To configure network accounting for CEFv6 and dCEFv6, use the following command in global configuration mode:
To verify that CEFv6 and network accounting for CEFv6 have been enabled globally on a nondistributed architecture platform, and that CEFv6 has been enabled on an IPv6 interface, enter the show running-config EXEC command. The following output shows that both that CEFv6 and network accounting for CEFv6 have been enabled globally on the router, and that CEFv6 has also been enabled on Ethernet interface 0.
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Note Configure the forwarding of IPv6 unicast datagrams globally on the router by using the ipv6 unicast-routing global configuration command, an IPv6 address on the interface by using the ipv6 address interface configuration command, and CEFv4 globally on the router by using the ip cef global configuration command before you can configure CEFv6 and network accounting for CEFv6. |
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Note Display text was omitted from the output. |
To verify that dCEFv6 and network accounting for dCEFv6 have been enabled globally on a distributed architecture platform, such as the Cisco 7500 series routers, use the show running-config EXEC command. The following example shows that both dCEFv6 and network accounting for CEFv6 have been enabled globally on the router.
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Note Configure the forwarding of IPv6 unicast datagrams globally on the router by using the ipv6 unicast-routing global configuration command and configure dCEFv4 globally on the router by using the ip cef distributed global configuration command before you can configure dCEFv6 and network accounting for CEFv6. |
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Note dCEFv6 is enabled by default on the Cisco 12000 series Internet routers and disabled by default on the Cisco 7500 series routers. Therefore, output from the show running-config EXEC command on the Cisco 12000 series does not show whether dCEFv6 is configured globally on the router. The following output is from a Cisco 7500 series router. |
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Note Display text was omitted from the output. |
In the following example, both CEFv6 and network accounting for CEFv6 have been enabled globally on a nondistributed architecture router, and CEFv6 has been enabled on Ethernet interface 0. The example also shows that the forwarding of IPv6 unicast datagrams has been configured globally on the router with the ipv6 unicast-routing global configuration command, an IPv6 address has been configured on Ethernet interface 0 with the ipv6 address interface configuration command, and CEFv4 has been configured globally on the router with the ip cef global configuration command.
In the following example, both dCEFv6 and network accounting for dCEFv6 have been enabled globally on a distributed architecture router. The example also shows that the forwarding of IPv6 unicast datagrams has been configured globally on the router with the ipv6 unicast-routing global configuration command and that dCEFv4 has been configured globally on the router with the ip cef distributed global configuration command.
In Cisco IOS release 12.2(8)T or later releases, IPv6 Internet Control Message Protocol (ICMP) Rate Limiting implements a token bucket algorithm for limiting the rate at which IPv6 ICMP error messages are sent out on the network. The initial implementation of IPv6 ICMP rate limiting defined a fixed interval between error messages, but some applications, such as traceroute, often require replies to a group of requests sent in rapid succession. The fixed interval between error messages is not flexible enough to work with applications such as traceroute and can cause the application to fail. Implementing a token bucket scheme allows a number of tokens—representing the ability to send one error message each—to be stored in a virtual bucket. The maximum number of tokens allowed in the bucket can be specified, and for every error message to be sent, one token is removed from the bucket. If a series of error messages is generated, error messages can be sent until the bucket is empty. When the bucket is empty of tokens, IPv6 ICMP error messages are not sent until a new token is placed in the bucket. The token bucket algorithm does not increase the average rate limiting time interval, and it is more flexible than the fixed time interval scheme.
The following sections explain how to configure the IPv6 ICMP Rate Limiting feature. Each task in the list is identified as either required or optional.
See the "IPv6 ICMP Rate Limiting Configuration Example" section for a configuration example.
To configure the interval and bucket size for IPv6 ICMP error messages, use the following command in global configuration mode:
Enter the show ipv6 traffic EXEC command to display ICMP rate-limited counters:
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Note For a description of each output display field, refer to the show ipv6 traffic command in the IPv6 for Cisco IOS Software, File 3 of 3: Commands document. |
The following example shows an interval of 50 milliseconds and a bucket size of 20 tokens being configured for IPv6 ICMP error messages:
The tasks in the following sections explain how to configure the Static Cache Entry for IPv6 Neighbor Discovery feature. Each task in the list is identified as either required or optional:
See the "Static Cache Entry for IPv6 Neighbor Discovery Configuration Example" section for a configuration example.
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Note Refer to the Start Here: Cisco IOS Software Release Specifics for IPv6 Features document for Cisco IOS software release specifics for supported IPv6 features. |
The Cisco IOS software uses static entries in the IPv6 neighbor discovery cache to translate 128-bit IPv6 addresses into 48-bit hardware addresses (functionality in IPv6 that is equivalent to static Address Resolution Protocol (ARP) entries in IPv4, which are used to translate 32-bit IP addresses into 48-bit hardware addresses).
To configure a static entry in the IPv6 neighbor discovery cache, use the following command in global configuration mode:
To display IPv6 neighbor discovery cache information, use the show ipv6 neighbors EXEC command. A hyphen (-) in the Age field of the command output indicates a static entry. The following example displays IPv6 neighbor discovery cache information for Ethernet interface 2:
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Note For a description of each output display field, refer to the show ipv6 neighbors command in the IPv6 for Cisco IOS Software, File 3 of 3: Commands document. |
The following example configures a static entry in the IPv6 neighbor discovery cache for a neighbor with the IPv6 address 3001:001::45a and link-layer address 0002.7d1a.9472 on Ethernet interface 1:
The IPv6 Duplicate Address Detection feature verifies the uniqueness of new unicast IPv6 addresses before assigning the addresses to interfaces (the new addresses remain in a tentative state while duplicate address detection is performed). Duplicate address detection uses neighbor solicitation messages to verify the uniqueness of unicast IPv6 addresses.
There are no required configuration tasks for the IPv6 Duplicate Address Detection feature; duplicate address detection on tentative unicast IPv6 addresses and the automatic sending of consecutive neighbor solicitation messages during duplicate address detection are enabled by default. However, the number of consecutive neighbor solicitation messages that are sent on an interface while duplicate address detection is performed on tentative unicast IPv6 addresses can be configured.
The tasks in the following sections explain how to configure the number of consecutive neighbor solicitation messages that are sent on an interface while duplicate address detection is performed on tentative unicast IPv6 addresses. Each task in the list is identified as either required or optional:
See the "IPv6 Duplicate Address Detection Configuration Example" section for a configuration example.
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Note Refer to the Start Here: Cisco IOS Software Release Specifics for IPv6 Features document for Cisco IOS software release specifics for supported IPv6 features. |
To configure the number of consecutive neighbor solicitation messages that are sent on an interface while duplicate address detection is performed on tentative unicast IPv6 addresses, use the following command in interface configuration mode:
To view the state (OK, TENTATIVE, or DUPLICATE) of the unicast IPv6 addresses configured for an interface, to verify whether duplicate address detection is enabled on the interface, and to verify the number of consecutive duplicate address detection, neighbor solicitation messages that are being sent on the interface, enter the show ipv6 interface EXEC command. The following example shows duplicate address detection specifics for Ethernet interface 0: