IP Addresses and Services Configuration Guide for Cisco 8000 Series Routers, IOS XR Releases

Shortened IPv6 routing prefixes

Updated: August 12, 2026

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Explains how shortening wide IPv6 prefixes improves LPM memory use and mitigates out-of-resource conditions. Covers operation, platform restrictions, configuration, reload, and verification.

Shortened IPv6 routing prefixes are wide prefixes that the router stores in a shorter LPM representation to

reduce the number of LPM entries used by prefixes longer than 64 bits
accommodate more wide IPv6 routing prefixes, and
mitigate out-of-resource conditions on supported hardware.

Table 1. Feature History Table
Feature Name	Release Information	Description
Shortened IPv6 Routing Prefixes	Release 25.4.1	Introduced in this release on: Fixed Systems (010 [ASIC: A100], 8700 [ASIC: K100])(select variants only) This feature is supported on: 8711-48Z-M 8011-32Y8L2H2FH 8011-12G12X4Y-A/D
Shortened IPv6 Routing Prefixes	Release 25.1.1	Introduced in this release on: Fixed Systems (8700 [ASIC: K100], 8010 [ASIC: A100])(select variants only*) This feature is supported on: 8712-MOD-M 8011-4G24Y4H-I
Shortened IPv6 Routing Prefixes	Release 24.4.1	Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100])(select variants only); Modular Systems (8800 [LC ASIC: P100])(select variants only) *This feature is supported on: 8212-48FH-M 8711-32FH-M 88-LC1-36EH 88-LC1-12TH24FH-E 88-LC1-52Y8H-EM
Shortened IPv6 Routing Prefixes	Release 24.1.1	We've improved the memory utilization of the Longest Prefix Match (LPM) table, allowing you to accommodate more IPv6 routing prefixes with wider IPv6 prefix lengths by storing them as shorter routing prefixes. This approach conserves router resources by reducing the number of entries in the routing table and is particularly helpful in mitigating out-of-resource (OOR) situations. This feature is supported only on Cisco Silicon One Q200-based routers and line cards. This feature modifies the hw-module profile route scale command with the new lpm wide-entries shortened keyword.

How shortened IPv6 routing prefixes work

An IPv6 address is 128 bits long and contains a routing prefix, subnet ID, and interface ID. The LPM table stores routing-prefix bits for forwarding decisions.

Summary

The router uses the LPM entry to determine the egress interface and next destination for a packet.

Workflow

These stages describe shortened-prefix storage:

The router receives an IPv6 route with a prefix longer than 64 bits.
The enabled hardware profile converts the wide prefix into a shorter routing-prefix representation.
The router stores the shortened representation in the LPM table and uses it for forwarding lookup.

Result

The LPM table accommodates more wide IPv6 routes with the available resources.

Guidelines and restrictions of shortened IPv6 routing prefixes

Reload the router after you enable shortened IPv6 routing prefixes.
Use the feature only on supported Cisco Silicon One Q200-based routers and line cards.
Do not enable IPv6 prefix scale expansion with shortened IPv6 routing prefixes.
Do not enable unicast Reverse Packet Forwarding (uRPF) with shortened IPv6 routing prefixes.

Configure shortened IPv6 routing prefixes

Reduce the LPM resources used by IPv6 prefixes longer than 64 bits.

Before you begin

Confirm that the router or line card uses supported Cisco Silicon One Q200 hardware.

Procedure

Enable shortened wide entries in global configuration mode.

Example:

Router# configure
Router(config)# hw-module profile route scale lpm wide-entries shortened
Router(config)# commit

Reload all locations.
Example:
```
Router# reload location all
```

Verify the route-scale profile.

Example:

Router# show hw-module profile route-scale
--------------------------------------------------------------
Knob                          Status          Applied   Action         
--------------------------------------------------------------
Wide-Entries-Shortened  Configured   Yes     None

The route-scale profile reports that shortened wide entries are configured and applied.

What to do next

To disable the feature, remove the profile with the no form of the command and reload all locations.

Need help?

Open a support case

(Requires a Cisco Service Contract)

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