Catalyst 3850 QoS Troubleshooting Commands

You would expect to have a very simple and intuitive QoS troubleshooting toolkit on a native MQC platform. Well, the first thing that came into my mind after I’ve been told that Catalyst 3850 is a proper MQC platform was something like

Wow, finally I can use the very same range of ISR commands to troubleshoot QoS on a hardware switching platform!

Unfortunately, that ended up to be a hybrid implementation. Yes, we have to use MQC to configure QoS on Catalyst 3850, including queuing! No, you are unlikely to solely use MQC commands to troubleshoot QoS. Remember that show mls qos commands range on Catalyst 3750 platform? It’s still the same candy, in a different wrapping though.

A “native” MQC Catalyst 3850 platform has the following commands, and you must remember them well:

  • show platform qos queue stats <interface name> <interface-id>

This is very useful command to confirm how many packets have been enqueued and dropped by different queue/threshold pairs.

SWITCH#show platform qos queue stats GigabitEthernet 1/0/39
DATA Port:11 Enqueue Counters
-------------------------------
Queue Buffers Enqueue-TH0 Enqueue-TH1 Enqueue-TH2
----- ------- ----------- ----------- -----------
    0       0           0           0    24343105
    1       0           0           0           0
    2       0     2377634           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  4707578537
DATA Port:11 Drop Counters
-------------------------------
Queue Drop-TH0    Drop-TH1    Drop-TH2    SBufDrop    QebDrop
----- ----------- ----------- ----------- ----------- -----------
    0           0           0           0           0           0
    1           0           0           0           0           0
    2           0           0           0           0           0
    3           0           0           0           0           0
    4           0           0           0           0           0
    5           0           0           0           0           0
    6           0           0           0           0           0
    7           0           0           0           0           0
 AQM Broadcast Early WTD COUNTERS(In terms of Bytes)
--------------------------------------------------
  PORT TYPE          ENQUEUE             DROP
--------------------------------------------------
 UPLINK PORT-0        N/A               0
 UPLINK PORT-1        N/A               0
 UPLINK PORT-2        N/A               0
 UPLINK PORT-3        N/A               0
 NETWORK PORTS      217428            1087140
 RCP PORTS               0                  0
 CPU PORT                0                  0
Note: Queuing stats are in bytes
  • show platform qos queue config <interface name> <interface-id>

Less intuitive command, which shows hardware interpretation of show policy-map interface output command. It does show modes in which different queues operate and hardware weights for all configured thresholds. You’re likely not going to use this one quite often.

SWITCH#sho platform qos queue config GigabitEthernet 1/0/39
DATA Port:11 GPN:39 AFD:Disabled QoSMap:1 HW Queues: 88 - 95
  DrainFast:Disabled PortSoftStart:1 - 600
----------------------------------------------------------
  DTS Hardmax   Softmax  PortSMin GlblSMin  PortStEnd
  --- --------  -------- -------- --------- ---------
 0   1  6    39  8   156  0   104   0    0   0   800
 1   1  6    39  8   156  0   104   0    0   0   800
 2   1  4     0  8   156  3   104   3   39   3   800
 3   1  4     0  9    39  3   104   3   39   3   800
 4   1  4     0 10    36  4    96   4   36   4   800
 5   1  4     0 10    36  4    96   4   36   4   800
 6   1  4     0 10    36  4    96   4   36   4   800
 7   1  4     0 11   144  4    96   4   36   4   800
 Priority   Shaped/shared   weight  shaping_step
 --------   ------------   ------  ------------
 0      1   Shaped            2047         204
 1      2   Shaped            1023         204
 2      7   Shared             125           0
 3      7   Shared              62           0
 4      7   Shared              62           0
 5      7   Shared              62           0
 6      7   Shared             250           0
 7      7   Shared              50           0
  Weight0 Max_Th0 Min_Th0 Weigth1 Max_Th1 Min_Th1 Weight2 Max_Th2 Min_Th2
  ------- ------- ------ ------ ------ ------ ------ ------ ------
 0     0     152      0      0    173      0      0    195       0
 1     0     152      0      0    173      0      0    195       0
 2     0     138      0      0    156      0      0    156       0
 3     0      30      0      0     34      0      0     39       0
 4     0      27      0      0     31      0      0     36       0
 5     0      27      0      0     31      0      0     36       0
 6     0      27      0      0     31      0      0     36       0
 7     0     114      0      0    128      0      0    144       0
  • show platform qos dscp-cos counters <interface name> <interface-id>

This command displays information identical to show mls qos interface <interface name-id> statistics on Catalyst 3750. It shows what DSCP and CoS values have been seen on a port in Ingress and Egress direction. Very useful when you need to confirm if PC or phone is marking packets according to your expectations / design.

SWITCH#show platform qos dscp-cos counters GigabitEthernet 1/0/39
Ingress DSCP0 15319030     0
--cut for brevity--
Ingress DSCP44 0           0
Ingress DSCP45 0           0
Ingress DSCP46 205446      0
Ingress DSCP47 0           0
Ingress DSCP48 0           0
Ingress DSCP49 2131477     0
Ingress DSCP50 0           0
--cut for brevity--
Ingress COS0 17976892      0
--cut for brevity--
Egress DSCP24 179425       0
Egress DSCP25 0            0
--cut for brevity--

As you may see, this output explicitly says that 2131477 packets on ingress were marked with DSCP 49. In our environment this corresponds to Lync Voice (we use custom markings applied using GPO to address Wireless QoS issues – this is re-marked to DSCP 46 on ingress).

Hope you find this useful.

 

3 Comments

  1. najmshah says:

    I could do this on MLS but not on MCQ switches.Looked for this command for months..nowhere is cisco docs.
    All i have to say…thanks very much

  2. David K says:

    Great article. are you able to explain what Drop-TH2 is?

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