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Overview of CoS Upgrade Requirements (Junos OS Release 11.1 or 11.2 to a Later Release)

Before you upgrade to Junos OS Release 11.3, you must deactivate the CoS configuration if the CoS configuration includes any of the following features:

  • excess-rate option

  • strict-high or high priority queues

  • Any of the Junos OS Release 11.1 or 11.2 default multidestination forwarding classes


If your CoS configuration contains any of the features listed above and you attempt to upgrade from Junos OS Release 11.1 or 11.2 to a later version without first editing the configuration, the Junos OS might not restart.

Junos OS Release 11.3 and later for QFX Series no longer supports the excess-rate statement, the strict priority option, or the default multidestination forwarding classes used in Junos OS Release 11.1 and 11.2. In addition, Junos OS Release 11.3 introduces new restrictions on how to configure and use strict-high priority queues.

This topic does not describe how to perform the software upgrade procedure. It describes how to deactivate your CoS configuration, edit your CoS configuration, and reactivate your CoS configuration at the appropriate times.

Use the following procedure to upgrade safely from Junos OS Release 11.1 or 11.2 to a later release:

  1. Deactivate the CoS configuration before you upgrade the software:

  2. Follow the upgrade procedure to Junos OS Release 11.3 or later software.

  3. Make the following changes to the CoS configuration while the CoS configuration is still deactivated:

    • Remove the excess-rate statement from the CoS configuration if you have used it at the [edit class-of-service schedulers] or [edit class-of-service traffic-control-profiles] hierarchy level.

    • Remove the strict-high and strict priority queue configurations if you have used them at the [edit class-of-service schedulers] hierarchy level.

    • Remove the default multidestination forwarding classes (mcast-be, mcast-af, mcast-ef, and mcast-nc) if you have used them at the [edit class-of-service schedulers], [edit class-of-service rewrite-rules], [edit class-of-service classifiers], [edit class-of-service scheduler-maps], or [edit class-of-service forwarding-class-sets] hierarchy level. Alternatively, you can change the mapping of the multidestination traffic to use the new default multidestination forwarding class (mcast).

  4. If desired, configure strict-high priority queues in accordance with the Junos OS Release 11.3 or later configuration rules, and map multidestination traffic to the default multidestination forwarding class (mcast).

  5. Activate the CoS configuration:

  6. Commit the CoS configuration:


If you configured the transmit-rate option for any queues under the [edit class-of-service schedulers] hierarchy level, if the rate is configured as an exact rate in Mbps, we recommend that you reconfigure the transmit-rate option as a percentage. This is because the scheduler converts exact rates to percentages, and when the exact rate is below 1 Gbps, some granularity may be lost in the conversion. You can avoid this potential issue by specifying the transmit-rate option as a percentage.