Outgoing DSCP values not being remapped

[mario.jost]

I have tried to configure QoS on our 2960X Switches. All interfaces have following configuration:

interface GigabitEthernet1/0/1
 switchport trunk native vlan 10
 switchport mode trunk
 mls qos trust dscp
 mls qos dscp-mutation COMPANY
 spanning-tree portfast trunk

The QoS configuation part on the switch is like follows:

mls qos map dscp-mutation COMPANY 1 2 3 4 5 6 7 8 to 0
mls qos map dscp-mutation COMPANY 9 10 11 12 13 14 15 16 to 0
mls qos map dscp-mutation COMPANY 17 18 19 20 21 22 23 24 to 0
mls qos map dscp-mutation COMPANY 25 26 27 28 29 30 31 33 to 0
mls qos map dscp-mutation COMPANY 34 35 36 37 38 39 40 41 to 0
mls qos map dscp-mutation COMPANY 42 43 44 45 47 48 49 50 to 0
mls qos map dscp-mutation COMPANY 51 52 53 54 55 56 57 58 to 0
mls qos map dscp-mutation COMPANY 59 60 61 62 63 to 0
mls qos map cos-dscp 0 0 0 0 32 46 0 0
mls qos

Thing is, we use DSCP 32 for citrix and DSCP 46 for voice. I want to trust DSCP only and dont work with the COS values. Thats why I rewrite possible COS values to respective DSCP. To keep an overview, I want to rewrite all "unused" DSCP values to 0. Thats why i have the DSCP mutation map in place on all interfaces. If i check the mls qos statistics on the interfaces, i see lots of different DSCP values on the ingress side. On the egress side, I should see only 0,32 and 46. This is true for all interfaces except the uplink port.

SWNFS010#show mls qos interface gigabitEthernet 1/0/26 statistics
GigabitEthernet1/0/26 (All statistics are in packets)

  dscp: incoming  
-------------------------------

  0 -  4 :  4284710630       524529            0            0         3505  
  5 -  9 :           1            0            0          586            1  
 10 - 14 :           0            0            0            0            0  
 15 - 19 :           0            0            0          458            0  
 20 - 24 :         111            0            0            0            0  
 25 - 29 :           1            0            0            0            0  
 30 - 34 :           0            0    118435078            0            1  
 35 - 39 :           0            0            0            0            0  
 40 - 44 :           0            0            0            0            0  
 45 - 49 :           0    114832289            0      1846661            0  
 50 - 54 :           0            0            0            0          154  
 55 - 59 :           0       656091            0            0            0  
 60 - 64 :           0            0            0            0  
  dscp: outgoing
-------------------------------

  0 -  4 :  4294291557            0            0            0            0  
  5 -  9 :           0            0            0            0            0  
 10 - 14 :           0            0            0            0            0  
 15 - 19 :           0            0            0            0            0  
 20 - 24 :           0            0            0            0            0  
 25 - 29 :           0            0            0            0            0  
 30 - 34 :           0            0      4821594            0            0  
 35 - 39 :           0            0            0            0            0  
 40 - 44 :           0            0            0            0            0  
 45 - 49 :           0      6152201            0       399188            0  
 50 - 54 :           0            0            0            0            0  
 55 - 59 :           0            0            0            0            0  
 60 - 64 :           0            0            0            0  
  cos: incoming  
-------------------------------

  0 -  4 :   430471196         8928        47649         7080    118467141  
  5 -  7 :   114834551       932493     26497035  
  cos: outgoing
-------------------------------

  0 -  4 :   448275170         3095        37247         2402         9464  
  5 -  7 :     6152833       400695      2389726  
  output queues enqueued:
 queue:    threshold1   threshold2   threshold3
-----------------------------------------------
 queue 0:     6152201           0           0
 queue 1:   481943491     1540023     2789871
 queue 2:       25836           0           0
 queue 3:         556           0           0

  output queues dropped:
 queue:    threshold1   threshold2   threshold3
-----------------------------------------------
 queue 0:           0           0           0
 queue 1:           0           0           0
 queue 2:           0           0           0
 queue 3:           0           0           0

Policer: Inprofile:            0 OutofProfile:            0

The incoming packets are marked with all sorts of DSCP, because the switch connected to it doesnt have the mutation map configured yet. But why are there outgoing DSCP 48 Packets on the switch?

FYI: Switch is running on lanbase-default sdm template and does not have ip routing activated. Configuration of affected port:

interface GigabitEthernet1/0/26
 switchport mode trunk
 mls qos trust dscp
 mls qos dscp-mutation COMPANY
end

Can you see something wrong in this setup? This is my fist time rolling out QoS from scratch. We dont have Cisco Phones in place and most of the manuals out there point towards using AutoQoS.

Thanks and best regards,
Mario

[chrihussey · Accepted solution]

The DSCP 48 counters you are seeing are probably control packets, most likely STP, generated by the switch and will be unaffected by the mutation map. By default Cisco assigns these packets CS6 (DSCP 48). Couldn't find this explicitly stated for the 2960, but from the 4500 config guide:

At the highest level, there are two types of locally sourced traffic (such as control protocol packets,pings, and telnets) from the switch: high priority traffic (typically the control protocol packets like OSPF Hellos and STP) and low priority packets (all other packet types).

High priority packets are marked as one of the following:

• internally with PAK_PRIORITY
• with IP Precedence of 6 (for IP packets)
• with CoS of 6 (for VLAN Tagged packets)