QOS config

[Asim Afzal]

Hi,

I have applied belpow config and after that i see lot of output drops on the interface.

Purpose of below config to mark packet with ip precdence 5 and set prioity percent 10

class-map match-any TO-MPLS-PLATINUM

match access-group name HC_COS_PBR

match precedence 5

policy-map TO-MPLS

class TO-MPLS-PLATINUM

  set ip precedence 5

  priority percent 10

class class-default

  queue-limit 50000 packets

  fair-queue

Can you advise me whats the best practice

Thanks

[mhnedirli]

Hello, Asim

your class map will chose traffic that matches HC_COS_PBR access list OR ip packets with precedence 5, under policy map you could define policy which you want to  make, in your example it is not necessary to set ip precedence 5 because you are matching packets with ip precedence 5.

priority percent 10 -> this command will prioritize traffic on your interface you could look LLQ for detailed information,

mark traffic as close as to the source, best practises are mark traffic on access layer and apply qos policy on distribution layers

[Joseph W. Doherty]

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Can you advise me whats the best practice

"Best practice" might be to not go configuring QoS features without understanding QoS.

Seriously, there's not really a single "best practice" although if you don't understand QoS well enough to customize it for your needs, Cisco recommendations (NB what they also use for the later AutoQoS) might be a good starting point.

Did you have lots of output drops before you activated this QoS configuration?

If so, your interface might just be oversubscribed, and QoS doesn't just make oversubscribed bandwidth drops vanish.  (Although with QoS you can better control traffic drop priority.)

Are the drops just since you enabled this QoS configuration?  If so, it might help if you would post policy map stats.  If the drops are in your Platinum class, you just might not have enough bandwidth allocated to LLQ, which acts as an implicit policer when there's congestion.

PS:

BTW a 50K queue limit in your class default seems a bit excessive.