CISCO IPv6 Generic Prefix User Manual

CISCO IPv6 Generic Prefix User Manual

IPv6 Generic Prefix
The IPv6 generic prefix feature simplifies network renumbering and allows for automated prefix definition. An IPv6 generic (or general) prefix (for example, /48) holds a short prefix, based on which a number of longer, more- specific prefixes (for example, /64) can be defined. When the general prefix is changed, all of the more-specific prefixes based on it will change, too.

• Finding Feature Information, page 1
• Information About IPv6 Generic Prefix, page 1
• How to Configure IPv6 Generic Prefix, page 2
• Additional References, page 4
• Feature Information for IPv6 Generic Prefix, page 5

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. 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 Generic Prefix

IPv6 General Prefixes
The upper 64 bits of an IPv6 address are composed of a global routing prefix plus a subnet ID, as defined in RFC 3513. A general prefix (for example, /48) holds a short prefix, based on which a number of longer, more-specific prefixes (for example, /64) can be defined. When the general prefix is changed, all of the more-specific prefixes based on it will change, too. This function greatly simplifies network renumbering and allows for automated prefix definition.For example, a general prefix might be 48 bits long (“/48”) and the more specific prefixes generated from it might be 64 bits long (“/64”). In the following example, the leftmost 48 bits of all the specific prefixes will be the same, and they are the same as the general prefix itself. The next 16 bits are all different.

• General prefix: 2001:DB8:2222::/48
• Specific prefix: 2001:DB8:2222:0000::/64
• Specific prefix: 2001:DB8:2222:0001::/64
• Specific prefix: 2001:DB8:2222:4321::/64
• Specific prefix: 2001:DB8:2222:7744::/64

General prefixes can be defined in several ways

• Manually
• Based on a 6to4 interface
• Dynamically, from a prefix received by a Dynamic Host Configuration Protocol (DHCP) for IPv6 prefix delegation client

More specific prefixes, based on a general prefix, can be used when configuring IPv6 on an interface.

How to Configure IPv6 Generic Prefix

Defining a General Prefix Manually
SUMMARY STEPS

1. enable
2. configure terminal
3. ipv6 general-prefix prefix-name {ipv6-prefix/prefix-length | 6to4 interface-type interface-number}

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 general-prefix prefix-name { ipv6-prefix/prefix- length

| 6to4 interface-type interface-number }

| Defines a general prefix for an IPv6 address.
| Command or Action| Purpose
---|---|---
| ****

Example:

Device(config)# ipv6 general-prefix my-prefix 2001:DB8:2222::/48

|

Using a General Prefix in IPv6

SUMMARY STEPS

1. enable
2. configure terminal
3. interface type number
4. ipv6 address {ipv6-address / prefix-length | prefix-name sub-bits/prefix-length

DETAILED STEPS

| Command or Action| Purpose
---|---|---
Step 1| enable

Example:

Router> enable

| Enables privileged EXEC mode.

•  Enter your password if prompted.

Step 2| configure terminal

Example:

Router# configure terminal

| Enters global configuration mode.
Step 3| ipv6 general-prefix prefix-name { ipv6-prefix

/ prefix-length | 6to4 interface-type interface-number

Example:

Router(config)# ipv6 general-prefix my-prefix 6to4 gigabitethernet 0/0/0

| Defines a general prefix for an IPv6 address.

When defining a general prefix based on a 6to4 interface, specify the 6to4 keyword and the interface-type interface-number arguments.

When defining a general prefix based on an interface used for 6to4 tunneling, the general prefix will be of the form 2001:a.b.c.d::/48, where “a.b.c.d” is the IPv4 address of the interface referenced.

| Command or Action| Purpose
---|---|---
Step 1| enable

Example:

Router> enable

| Enables privileged EXEC mode.

•  Enter your password if prompted.

Step 2| configure terminal

Example:

Router# configure terminal

| Enters global configuration mode.
Step 3| interface type number

Example:

Router(config)# interface gigabitethernet 0/0/0

| Specifies an interface type and number, and places the router in interface configuration mode.
Step 4| ipv6 address { ipv6-address / prefix-length | prefix-name sub-bits / prefix-length

Example:

Router(config-if) ipv6 address my-prefix 2001:DB8:0:7272::/64

| Configures an IPv6 prefix name for an IPv6 address and enables IPv6 processing on the interface.

Additional References

Related Documents

List,](http://www.cisco.com/en/US/docs/ios/mcl/allreleasemcl/all_book.html) All Releases
IPv6 commands| Cisco IOS IPv6 Command Reference
Cisco IOS IPv6 features| Cisco IOS IPv6 Feature Mapping

Standards and RFCs

List,](http://www.cisco.com/en/US/docs/ios/mcl/allreleasemcl/all_book.html) All Releases
IPv6 commands| Cisco IOS IPv6 Command Reference
Cisco IOS IPv6 features| Cisco IOS IPv6 Feature Mapping

MIBs

feature sets, use Cisco MIB Locator found at the following URL:

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

Technical Assistance

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 Generic Prefix

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

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

composed of a global routing prefix plus a subnet ID. A general prefix (for example,

/48) holds a short prefix, based on which a number of longer,

more-specific, prefixes (for

example, /64) can be defined.

The following commands were introduced or modified: ipv6 address , ipv6 general-prefix.

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