Cisco 3850-48XS-E many interfaces with mass output drops

[mtaddia]

Good morning,
we recently installed a stackwise-virtual of two Cisco 3850-48XS-E with SW Ver. 16.6.4 but we see several interfaces drops.
In the logging I find the following message:

%PLATFORM_MATM-4-QUEUE_OVERLIMIT: MATM dropped learn cache batch messages as queue limit has reached.
Is there a correlation between the drops and the log error message?
Attached show interfaces with drops.
thanks
Marco

[Deepak Kumar]

Hi,

Can you check your CPU uses as well? Is it updated IOS version? Please check a document:

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-6/release_notes/ol-16-6-3850.html

[Leo Laohoo]

That means QoS is configured incorrectly (or not at all).

[mtaddia]

we did not implement any qos policy but left the policy-maps and class-maps installed by default. The GigabitEthernet interfaces have no policy or class-map applied. See attached file. Many thanks

[Leo Laohoo]

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@mtaddia wrote:

we did not implement any qos policy 

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Unlike the Catalyst 2960, 3560/3750 (where they can operate without QoS), 3650/3850 REQUIRES QoS. 

Unfortunately, the QoS configuration for the 3650/3850 is very unforgiving.  If the configuration is off by a tiny mark you will get packet drops.  

[dreamingms]

Hi Leo, Do you know how to config minimum qos so that 3850 can work well, because I don't need qos actually.

[Georg Pauwen]

Hello,

try and globally configure:

qos queue-softmax-multiplier 1200

on the switches that have interfaces with output drops...

[mtaddia]

Thanks a lot Georg with the "qos queue-softmax-multiplier 1200" command, the reporting of the total output drops has almost disappeared on almost all the interfaces of the affected switches. Unfortunately, on some backbones,  output drops persist even if much less than before. Do you have any suggestions? Thanks again.

Marco

[dreamingms]

Hi ， mtaddia, I have the same problem with you . Have you solved the problem finally?