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QoS deployment

Hi All,

I want to deploy QoS in a campus network for future VoIP. I red a lot about it, but I can't figure out a few things. The questions are about a cisco catalyst 6500, which is the core of the campus.

-Is it the best practice to use "auto qos voip trust" on trusted uplink interfaces? I know there is a macro behind, which changes some bandwith ratios, tresholds etc for all interfaces on the same ASIC and adjusts the global cos-dscp mapping. But I can't find any recommendation. There must be a good reason for it, but why are these settings not default and active when you globally enable mls qos?

-Is priority scheduling enabled when there is no bandwith ratio filled in for queue 4 (1p3q8t)?

-If "mls qos trust cos" is configured on a trunked interface which transport l3 transit vlans with a dscp value set, would it use the dscp-cos mapping and leave the according cos value untouched?

Thanks in advance..



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