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  • 1.  CoS defaults on QFX switches

    Posted 08-27-2019 16:45

    Hi all,


    I'm configuring CoS on a QFX5100 for the first time and would appreciate some guidance around what happens to the default CoS components when you configure custom CoS components.


    For example, the QFX Traffic Management Guide states that "If you explicitly configure one type of classifier but not other types of classifiers, the system uses only the configured classifier and does not use default classifiers for other types of traffic." I'm using a BA classifier to assign traffic with certain DSCP markings to queue 5. Does this mean that I also need to explicity configure a default classifier to handle all other unicast and multicast traffic?


    Also, does configuring a custom scheduler overwrite the default schedulers in the default scheduler-map?


    Unfortunately I don't have access to a test environment where I can see the effect that my configuration changes will have, so any guidance / experiences would be appreciated!


  • 2.  RE: CoS defaults on QFX switches
    Best Answer

    Posted 08-28-2019 02:19

    Good Day,


    Yes, you understand it correctly.

    Once you replace default classifiers or schedulers with custom one, you should take care of all types of traffic, otherwise they will be deprived.

    JunOS has a hint "import default" for classifiers.

    "import default" will fill your custom classifier with action for all types of traffic, so no one gets deprived.

    Then you just add your own rules to the custom classifier, they will take precedence over default rules.


    Play wise with custom schedulers, consider all traffic types, give each of them enough bandwidth and buffer size.

    Tune it accordingly, if you see unexpected drops.


    Hope it helps!


  • 3.  RE: CoS defaults on QFX switches

    Posted 08-30-2019 01:29

    Thanks for that confirmation Pavel, much appreciated!