QoS - Trust DSCP on CoS-based Linecard

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Jan 29th, 2014
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How does the switch manage ingress queueing when I configure - trust dscp - on a port of a linecard that supports only cos-based queueing e.g. the WS-X6848-GE-TX on Catalyst 6500?

1) Does the switch ingress queueing according to the incoming CoS value in the packet (given that the packet has a 802.1q tag)


2) Does the switch ingress queueing according to the "internal" CoS value it gets from the DSCP-to-CoS map

According to the Catalyst 6500 Configuration Guide - Figure 43-3 - the switch does the queueing based on the incoming CoS value of the packet.


Can anybody confirm this?

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Jon Marshall Wed, 01/29/2014 - 04:38
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For PFC based QOS -


1) yes it does

2) the CoS value determined from the internal DCSP value is, as far as i am aware, only relevant to egress queueing.

Edit - for confirmation see Table 1 in the following link  -


i am not familiar with QOS on the 6500s using IOS 15.x so there may be differences.



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