cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
687
Views
0
Helpful
3
Replies

Cat6500 behavior with QoS disabled

WILLIAM KLEIN
Level 1
Level 1

Can someone answer this question for me? Will the 6500 strip or remark the DSCP markings in a packet with mls qos disabled?

Our phones mark their packets with a DSCP of 46. We want the switch to honor that marking and leave it untouched. By default, with QoS disabled, the ports trust the DSCP as shown below:

QoS is disabled globally

Trust state: trust DSCP

Extend trust state: not trusted [COS = 0]

So it trusts the incoming DSCP markings. Will it pass them thru the switch and leave them marked as DSCP 46?

Thanks for your help.

1 Accepted Solution

Accepted Solutions

wochanda
Level 4
Level 4

Yes, we will not re-mark packets when 'mls qos' is disabled.

View solution in original post

3 Replies 3

wochanda
Level 4
Level 4

Yes, we will not re-mark packets when 'mls qos' is disabled.

Thank you very much. That's what I wanted to hear.

darrenj
Level 1
Level 1

What I believe will happen here is that the DSCP will be left untouched, but no QOS will be applied to it. Therefore, the switch treats a packet marked with DSCP value 46 exactly the same as all other packets.

In most cases, people give QOS preference to packets such as DSCP 46 because they are more important (for example voice is more critical and not tolerent to jitter, as opposed to web traffic).

Getting back to your original question, with no QOS enabled, the DSCP value is ignored and passes out of the switch the same as it enters :-)

Dazzler

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: