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Output Drops on C9300

Consistently see output drops on TenGig interface (actually a 1GB fiber handoff using the TenGig SFP for MPLS) on a C9300 (16.9.1).  Auto QoS applied to interface and softmax-queue is at 1200 on switch as well.  Output from sh run int x/x/x, sh int x/x/x and sh policy-map int x/x/x below.  From what I can tell, the drops are occurring in the class default queue, so CS0 traffic I believe.  We are using WebEx Room Kits (dscp AF41) that occasionally have a degradation in call quality and the ingress/egress to source/destination is via this interface.  Packet captures have shown that the traffic for the Room Kits are UDP and bursty in nature.  With the output from sh policy-map and what is reported from end users on calls, I am not seeing drops from the correct queue.  Where else can I investigate to find root cause of the total output drops on this interface?  Appreciate any thoughts and ideas.  Thank you. 



interface TenGigabitEthernet1/1/1
description Link to XX circuit
switchport trunk allowed vlan x,x,x
switchport mode trunk
switchport nonegotiate
ip flow monitor xxxxxxx input
ip flow monitor xxxxxxx output
load-interval 30
auto qos trust dscp


#sh int te1/1/1 hum
TenGigabitEthernet1/1/1 is up, line protocol is up (connected)
Hardware is Ten Gigabit Ethernet, address is 6cdd.30ef.581d (bia 6cdd.30ef.581d)
Description: Link to xx circuit
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 4/255, rxload 3/255
Encapsulation ARPA, loopback not set
Keepalive not set
Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseSX SFP
input flow-control is on, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:03, output hang never
Last clearing of "show interface" counters 19:47:32
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 53478785
Queueing strategy: Class-based queueing
Output queue: 0/40 (size/max)
30 second input rate 13.26 mega-bits/sec , 4.47 Kpps
30 second output rate 18.54 mega-bits/sec , 5.13 Kpps
227,392,297 packets input, 94,867,305,256 bytes, 0 no buffer
Received 209,678 broadcasts (161,215 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 161,215 multicast, 0 pause input
0 input packets with dribble condition detected
592,500,567 packets output, 440,236,724,792 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
2,375 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out



#sh policy-map int te1/1/1

Service-policy input: AutoQos-ppm-Trust-Dscp-Input-Policy

Class-map: class-default (match-any)
245237044 packets
Match: any
QoS Set
dscp dscp table AutoQos-4.0-Trust-Dscp-Table

Service-policy output: AutoQos-ppm-Output-Policy

queue stats for all priority classes:
priority level 1

(total drops) 0
(bytes output) 3320094515

Class-map: AutoQos-ppm-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-ppm-Output-Control-Mgmt-Queue (match-any)
0 packets
Match: dscp cs2 (16) cs3 (24) cs6 (48) cs7 (56)
Match: cos 3

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) 13945849
bandwidth remaining 10%

queue-buffers ratio 10

Class-map: AutoQos-ppm-Output-Multimedia-Conf-Queue (match-any)
0 packets
Match: dscp af41 (34) af42 (36) af43 (38)
Match: cos 4

(total drops) 0
(bytes output) 1751968690
bandwidth remaining 10%
queue-buffers ratio 10

Class-map: AutoQos-ppm-Output-Trans-Data-Queue (match-any)
0 packets
Match: dscp af21 (18) af22 (20) af23 (22)
Match: cos 2

(total drops) 0
(bytes output) 197615796
bandwidth remaining 10%
queue-buffers ratio 10

Class-map: AutoQos-ppm-Output-Bulk-Data-Queue (match-any)
0 packets
Match: dscp af11 (10) af12 (12) af13 (14)
Match: cos 1

(total drops) 0
(bytes output) 19404909061
bandwidth remaining 4%
queue-buffers ratio 10

Class-map: AutoQos-ppm-Output-Scavenger-Queue (match-any)
0 packets
Match: dscp cs1 (8)

(total drops) 0
(bytes output) 0
bandwidth remaining 1%
queue-buffers ratio 10

Class-map: AutoQos-ppm-Output-Multimedia-Strm-Queue (match-any)
0 packets
Match: dscp af31 (26) af32 (28) af33 (30)

(total drops) 0
(bytes output) 4075465486
bandwidth remaining 10%
queue-buffers ratio 10

Class-map: class-default (match-any)
0 packets
Match: any

(total drops) 54552249
(bytes output) 415018269243
bandwidth remaining 25%
queue-buffers ratio 25

VIP Expert

Re: Output Drops on C9300

Have a look at this post. Maybe a negotiation issue with provider's router/switch.



Re: Output Drops on C9300

Thanks Reza.  I have seen that post in my research and will reach out to provider.  Ill also have someone on site at DC confirm we are using correct fiber handoff.  Its happened before with a point to point where the fiber was incorrect but was still working, with a lot of output drops, similar to what we are seeing here.  Sh inventory is showing correct SFP, sh int x/x/x transceiver detail shows good light.  What do you make of the sh policy-map output with the dropped traffic at the last queue?  Is that correct to assume that the traffic is CS0 and not related to WebEx?  Thank you.  


Re: Output Drops on C9300

ISP came back and stated that L1 & L2 checks were completed and no issues on the circuit.  Negotiation for duplex and speed are correct.  Fiber handoff, patch cable and SFP are good.  Next step for me would be to get a TAC case open to look at adjusting the queue-buffer ratio maybe.

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