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lb3 Beginner
Beginner

cisco 3850 16.3.7 qos default behavior

Hi All,

 

Trying to understand how the default queuing model works on a cisco 3850 when using limited markings.

 

For example: 

 

interfaces towards users:

service-policy input voice-in

 

interface towards svi on core

service-policy output voice-out

 

 

Policy Map voice-out
Class voice
set cos 5
set dscp ef

 

Policy Map voice-in
Class voice
set cos 5

 

Class Map match-any voice (id 6)
Match vlan XXX

 

 

show platform hardware fed switch 1 qos queue config interface gi x/x/x 
DATA Port:0 GPN:49 AFD:Disabled QoSMap:6 HW Queues: 0 - 7
DrainFast:Disabled PortSoftStart:2 - 6480
----------------------------------------------------------
DTS Hardmax Softmax PortSMin GlblSMin PortStEnd
--- -------- -------- -------- --------- ---------
0 1 6 720 7 2880 7 1280 0 0 6 8640
1 1 4 0 8 4320 8 1920 3 1080 6 8640
2 1 4 0 5 0 5 0 0 0 6 8640
3 1 4 0 5 0 5 0 0 0 6 8640
4 1 4 0 5 0 5 0 0 0 6 8640
5 1 4 0 5 0 5 0 0 0 6 8640
6 1 4 0 5 0 5 0 0 0 6 8640
7 1 4 0 5 0 5 0 0 0 6 8640
Priority Shaped/shared weight shaping_step
-------- ------------ ------ ------------
0 0 Shared 50 0
1 0 Shared 75 0
2 0 Shared 10000 0
3 0 Shared 10000 0
4 0 Shared 10000 0
5 0 Shared 10000 0
6 0 Shared 10000 0
7 0 Shared 10000 0

Weight0 Max_Th0 Min_Th0 Weigth1 Max_Th1 Min_Th1 Weight2 Max_Th2 Min_Th2
------- ------- ------ ------ ------ ------ ------ ------ ------
0 0 2868 0 0 3206 0 0 3600 0
1 0 3442 0 0 3847 0 0 4320 0
2 0 0 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0 0 0
4 0 0 0 0 0 0 0 0 0
5 0 0 0 0 0 0 0 0 0
6 0 0 0 0 0 0 0 0 0
7 0 0 0 0 0 0 0 0 0

 

 

With this configuration does all traffic all go to one queue or does it get put into different queues?  (reference: https://www.cisco.com/en/US/docs/solutions/Enterprise/Video/qoscampuscat3x50aag.pdf)

If it does get put into different queues does the traffic with markings go into P1 and everything else go into 1 of the remaining queues?

 

Looking at the following it looks like traffic is only going into 2 queues and there are some drops. I'm guessing the voice traffic is going into Queue 0 and not being dropped. How does the switch determine what traffic to drop out of everything that is going into Queue 1? I've been told, don't muck with the queue's as it's too much work, but there seems to be some good documentation on the internet on configuring the queues appropriately (see above link)

 

show platform hardware fed switch 1 qos queue stats interface gi x/x/x 
DATA Port:0 Enqueue Counters
-------------------------------
Queue Buffers Enqueue-TH0 Enqueue-TH1 Enqueue-TH2
----- ------- ----------- ----------- -----------
0 0 0 5094608996 285513150
1 0 0 0 5696016827
2 0 0 0 0
3 0 0 0 0
4 0 0 0 0
5 0 0 0 0
6 0 0 0 0
7 0 0 0 0

 

I always thought you had to associate traffic to a queue. I guess there is a default association ?

 

Just trying to further my qos knowledge.

 

Thanks!

 

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