10-19-2005 10:43 AM - edited 03-03-2019 12:29 AM
Platform - Catalyst 3560.
IOS - 12.2(25)SEC2
TEST(config)#no mls qos
TEST(config)#mls qos rewrite ip dscp
TEST(config)#end
TEST#sh mls qos
QoS is disabled
QoS ip packet dscp rewrite is enabled
Will this disable all QoS functions except for changing all DSCP values to 0? It seems strange that the switch would allow the command "mls qos rewrite ip dscp" after "no mls qos" if there were no effect. It would also seem logical that without "mls qos", "mls rewrite ip dscp" would be rendered useless.
10-19-2005 10:54 AM
With mls qos disabled , all the ports are in "trusted" state which means the switch will not change the dscp whatsoever. So even having the "mls qos rewrite ip dscp" should not have any effect when the qos is disabled. It does not really matter that you have this command or not , whats important is the port trust state and thats always "trusted" when qos is disabled and this is true for all switching platforms.
Thanks
Salman Z.
10-19-2005 11:04 AM
Thanks for the quick reply.
My biggest concern is that by simply issuing the command "mls qos" performance on large file transfers almost doubles. I'm not a great QoS mind by any means.
Do I need to adjust ingress or egress queues? My queue sets are posted below. I want to be certain that all DSCP is set to 0 while maintaining performance as much as possible.
TEST(config)#mls qos
TEST(config)#mls qos rewrite ip dscp
TEST(config)#exit
TEST#sh mls qos queue-set
Queueset: 1
Queue : 1 2 3 4
----------------------------------------------
buffers : 25 25 25 25
threshold1: 100 200 100 100
threshold2: 100 200 100 100
reserved : 50 50 50 50
maximum : 400 400 400 400
Queueset: 2
Queue : 1 2 3 4
----------------------------------------------
buffers : 25 25 25 25
threshold1: 100 200 100 100
threshold2: 100 200 100 100
reserved : 50 50 50 50
maximum : 400 400 400 400
TEST#
Thanks again!
10-19-2005 08:57 PM
Its best to leave the qos settings at default. If you are running anything lower then 12.2(25)SEB , then be aware of CSCeg29704. By enabling qos , since the port goes to untrusted state , all dscps will be rewritten to 0. So just by enabling qos , you will get what you want . Although it surprises me that just by enabling qos , you are getting double the performance w/o enabling any kind of classification.
Thanks
Salman Z.
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