Modular QoS Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Release

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Modular QoS Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Release

VOQ CGM profile prefitting

Updated: June 9, 2026

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Explains how VOQ congestion-management profile prefitting optimizes queue-limit scalability and enables interoperability across supported Cisco 8000 platforms.

VOQ congestion-management (CGM) profile prefitting is a resource-optimization feature that

maps configured queue-limit values to predefined hardware-supported profiles, and
uses a unified VOQ CGM profile allocation model across supported platforms operating in compatibility mode.

VOQ CGM profile prefitting applies to queue-limit (QL), dual queue-limit (DQL), and Random Early Detection (RED) congestion-management configurations.

Table 1. Feature History Table
Feature Name	Release Information	Feature Description
VOQ CGM profile prefitting	Release 26.2.1	Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100]; Modular Systems (8800 [LC ASIC: P100]) Now you can use a unified VOQ CGM profile allocation model improving interoperability between K100 and P100 line cards for QL, DQL, and RED configurations. This feature introduces the prefit model for P100 line cards, maps QL configurations to reserved prefit profiles, and provides 12 dedicated custom profiles for DQL and RED.

Benefits of VOQ CGM profile prefitting

Enables interoperability between supported K100, P100, and P200 platforms operating in P100 NPU compatibility mode.
Improves queue-limit scale by mapping configured queue-limit values to predefined profiles instead of consuming a unique profile for every configured queue-limit value.
Provides a dedicated custom profile pool for DQL and RED configurations.

VOQ CGM profile allocation and queue-limit prefitting behavior

Starting with Cisco IOS XR Release 26.2.1, the router supports a maximum of 12 shared VOQ CGM profiles for DQL, RED, and ECN to enable interoperability across K100, P100, and P200 ASIC-based systems. In this release, configured QL values are automatically mapped to predefined hardware-supported queue-limit profiles, which can result in deviations between configured and operational QL values.

Previously, VOQ CGM profiles were allocated on a first-come, first-served basis, and configured queue-limit values were applied directly without hardware prefitting.

Table 2. Queue-limit and custom profile behavior
Configuration type	Behavior
Queue-limit	Mapped to predefined hardware-supported queue-limit profiles.
DQL and RED	Allocated from the custom VOQ CGM profile pool. The system supports a maximum of 12 custom profiles.

Usage guidelines for VOQ CGM profile prefitting

Monitor custom profile usage for DQL and RED

Keep the number of unique DQL and RED profile combinations within the supported custom VOQ CGM profile scale.

In P100 NPU compatibility mode, the router supports a maximum of 12 custom VOQ CGM profiles for DQL and RED configurations across the system. If the required DQL and RED profile combinations exceed the available custom profile scale, the configuration commit can fail.

Use the show ofa objects tmrateprofile object-count location command to review profile usage.

Upgrade considerations

Before you upgrade to Cisco IOS XR Release 26.2.1, review QoS policies that use multiple unique DQL or RED configurations.

Starting from Release 26.2.1, VOQ CGM profile prefitting is enabled by default in P100 NPU compatibility mode, and only 12 custom profiles are available for DQL and RED configurations across the system. Configurations that require more than 12 custom DQL or RED profiles can fail during or after upgrade because additional custom VOQ CGM profiles are not available. If the deployment uses only P100 platforms and does not require interoperability with K100 or P200 platforms, you can disable VOQ CGM profile prefitting to use the legacy profile allocation behavior.

Use legacy mode only for P100-only deployments

Disable VOQ CGM profile prefitting only when the system uses P100 platforms and interoperability with K100 or P200 platforms is not required.

The legacy mode reverts P100 platforms to the previous first-come, first-served VOQ CGM profile allocation behavior and disables prefitting. K100 and P200 line cards are not supported in this mode. After you disable VOQ CGM profile prefitting and reload the chassis, P100 platforms use the legacy non-prefit allocation model.

Use the hw-module profile qos voq-cgm-prefit disable command to disable VOQ CGM profile prefitting, and then reload the chassis for the change to take effect.

Disable VOQ CGM profile prefitting

Disable VOQ CGM profile prefitting to use the legacy VOQ CGM profile allocation behavior on supported platforms.

Use this task only when the deployment does not require interoperability with K100 or P200 platforms. K100 and P200 line cards are not supported when VOQ CGM profile prefitting is disabled.

After you configure the command, reload the chassis for the change to take effect.

Procedure

	1.	Disable VOQ CGM profile prefitting. Example: `Router(config)#hw-module profile qos voq-cgm-prefit disable Router(config)#commit` The router displays a message that a manual chassis reload is required to activate or deactivate the VOQ CGM profile prefitting configuration.
	2.	Verify the configured and applied state. Example: `Router#show hw-module voq-cgm-prefit` Before the chassis reload, the command output can show the configuration as pending and list the required action as `Reload`. Example before reload: `Location Configured Applied Action ---------------------------------------------------------------------------- 0/RP0/CPU0 Yes No Reload` After the chassis reload, the command output shows that the configuration is applied. Example after reload: `Location Configured Applied Action ---------------------------------------------------------------------------- 0/RP0/CPU0 Yes Yes N/A`

VOQ CGM profile prefitting is disabled, and the router uses the legacy non-prefit VOQ CGM profile allocation behavior on supported platforms.

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