I'm using a Cisco 9300 with IOS XE 16.09, and I found something strange: Output drops. And I think that these output drops are related to AutoQoS.
This is the interface configuration:
interface GigabitEthernet1/0/1 switchport access vlan 415 switchport mode access switchport nonegotiate switchport voice vlan 789 auto qos trust spanning-tree portfast service-policy input AutoQos-4.0-Trust-Cos-Input-Policy service-policy output AutoQos-4.0-Output-Policy end
To each port is a PC or laptop (docking station) connected and a Yealink VoIP phone. The PC/ laptop is connected to the phone, and the phone is connected to the port.
This is the policy map that is attached to all interfaces:
9300-1#sh policy-map int gi1/0/1 GigabitEthernet1/0/1 Service-policy input: AutoQos-4.0-Trust-Cos-Input-Policy Class-map: class-default (match-any) 327161029 packets Match: any QoS Set cos cos table AutoQos-4.0-Trust-Cos-Table Service-policy output: AutoQos-4.0-Output-Policy queue stats for all priority classes: Queueing priority level 1 (total drops) 0 (bytes output) 399130526 Class-map: AutoQos-4.0-Output-Priority-Queue (match-any) 0 packets Match: dscp cs4 (32) cs5 (40) ef (46) Match: cos 5 Priority: 30% (300000 kbps), burst bytes 7500000, Priority Level: 1 Class-map: AutoQos-4.0-Output-Control-Mgmt-Queue (match-any) 0 packets Match: dscp cs2 (16) cs3 (24) cs6 (48) cs7 (56) Match: cos 3 Queueing queue-limit dscp 16 percent 80 queue-limit dscp 24 percent 90 queue-limit dscp 48 percent 100 queue-limit dscp 56 percent 100 (total drops) 0 (bytes output) 12987888 bandwidth remaining 10% queue-buffers ratio 10 Class-map: AutoQos-4.0-Output-Multimedia-Conf-Queue (match-any) 0 packets Match: dscp af41 (34) af42 (36) af43 (38) Match: cos 4 Queueing (total drops) 0 (bytes output) 0 bandwidth remaining 10% queue-buffers ratio 10 Class-map: AutoQos-4.0-Output-Trans-Data-Queue (match-any) 0 packets Match: dscp af21 (18) af22 (20) af23 (22) Match: cos 2 Queueing (total drops) 0 (bytes output) 0 bandwidth remaining 10% queue-buffers ratio 10 Class-map: AutoQos-4.0-Output-Bulk-Data-Queue (match-any) 0 packets Match: dscp af11 (10) af12 (12) af13 (14) Match: cos 1 Queueing (total drops) 0 (bytes output) 0 bandwidth remaining 4% queue-buffers ratio 10 Class-map: AutoQos-4.0-Output-Scavenger-Queue (match-any) 0 packets Match: dscp cs1 (8) Queueing (total drops) 0 (bytes output) 0 bandwidth remaining 1% queue-buffers ratio 10 Class-map: AutoQos-4.0-Output-Multimedia-Strm-Queue (match-any) 0 packets Match: dscp af31 (26) af32 (28) af33 (30) Queueing (total drops) 0 (bytes output) 0 bandwidth remaining 10% queue-buffers ratio 10 Class-map: class-default (match-any) 0 packets Match: any Queueing (total drops) 41326851 (bytes output) 18995900759 bandwidth remaining 25% queue-buffers ratio 25
I see dropped packets on all active ports, and it looks like that traffic, that traffic matches either class map "AutoQos-4.0-Output-Control-Mgmt-Queue" or class map "class-default". And only traffic that matches "class-default" is being dropped.
Do you share this observation? I can't see that traffic is dropped due to physical errors or congestion.
Any explanation for this? I'm new to Cisco and this switch was configured by another admin, that isn't onboard anymore. :/ Thanks for advice!
your understanding is correct.
You say that you are new to Cisco devices.
The AutoQoS provides an automatic configuration and deployment using parameters that are considered best practice for common scenarios.
However, the AutoQoS is not a perfect fit for every environment and you may need and you can actually do a tuning of the configuration.
First of all, the VOIP traffic should be classified in the priority queue and you say you see traffic only in two classes.
You need to read the following documents:
! for auto-qos
It is not an easy argument feel free to ask for help.
Hope to help
thank you for your reply and for confirming my observation. If I understand your posting correctly, VoIP packets should be addressed by class map "AutoQos-4.0-Output-Priority-Queue", which is currently getting no traffic. Correct? I miss the
(total drops) (bytes output)
rows for "AutoQos-4.0-Output-Priority-Queue" in the output, which makes me think that this class map matches no traffic.
Thank you for your help!