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QoS on Catalyst 3850: are class-map statistics really per interface? (show policy-map interface)

Hi, I am puzzled about the QoS statistics on the Cisco Catalyst 3850 (model 3850-12XS), software version 03.07.05E. The CLI command "show policy-map interface" provides class-map statistics for each interface. Below is an output example of this command (real output snippet from my switch).

 

As you can see it is a stack of two 3850 switches, so the interface IDs are Te1/0/x (Te1/0/1 to Te1/0/12) and Te2/0/x (Te2/0/1 to To2/0/12). FYI in case it should matter: each port is configured in a port-channel across both switches: Te1/0/1 + Te2/0/1, Te1/0/2 + Te2/0/2, Te1/0/3 + Te2/0/3, etc.

 

But what I don't understand is: the 'packets' counters for each class-map are (as good as) identical for all interfaces on the same stack node. All Te1/0/x interfaces have identical packets counters and all Te2/0/x interfaces have identical packets counters!

 

This doesn't seem normal behaviour to me, or am I missing something?
Since the output of the command is listed per interface, I assume the counters should also be interface specific and not the same for each interface, no?


hostname#show policy-map interface
TenGigabitEthernet1/0/1
Service-policy input: pm-in-marking
Class-map: class-in-realtime (match-any)
624574798 packets
Class-map: class-in-buscrit (match-any)
554030082 packets
Class-map: class-default (match-any)
26851783296 packets
Match: any

TenGigabitEthernet1/0/2
Service-policy input: pm-in-marking
Class-map: class-in-realtime (match-any)
624574798 packets
Class-map: class-in-buscrit (match-any)
554030082 packets
Class-map: class-default (match-any)
26851783296 packets
Match: any

TenGigabitEthernet1/0/3
Service-policy input: pm-in-marking
Class-map: class-in-realtime (match-any)
624577296 packets
Class-map: class-in-buscrit (match-any)
554031562 packets
Class-map: class-default (match-any)
26851841398 packets
Match: any

TenGigabitEthernet2/0/1
Service-policy input: pm-in-marking
Class-map: class-in-realtime (match-any)
482963561 packets
Class-map: class-in-buscrit (match-any)
784046719 packets
Class-map: class-default (match-any)
13167926772 packets
Match: any

TenGigabitEthernet2/0/2
Service-policy input: pm-in-marking
Class-map: class-in-realtime (match-any)
482963561 packets
Class-map: class-in-buscrit (match-any)
784046719 packets
Class-map: class-default (match-any)
13167926772 packets
Match: any

TenGigabitEthernet2/0/3
Service-policy input: pm-in-marking
Class-map: class-in-realtime (match-any)
482963561 packets
Class-map: class-in-buscrit (match-any)
784046719 packets
Class-map: class-default (match-any)
13167926772 packets
Match: any

 

 

PS: the same symptom applies to statistics via SNMP: OID .1.3.6.1.4.1.9.9.166.1.15 = cbQosClassMapStats also provides the same packet counters for each interface (per stack node).

Everyone's tags (2)
6 REPLIES 6
Participant

Re: QoS on Catalyst 3850: are class-map statistics really per interface? (show policy-map interface)

Hi. i never noticed this but see the same thing. 

 

I always look at the bytes output / conformed bytes and these counters are different for each interface. 

 

Could be the matched packets are cumulative and the interface specific counters are bytes outpunt and conformed bytes. 

Re: QoS on Catalyst 3850: are class-map statistics really per interface? (show policy-map interface)

Hi thanks for the feedback.

You are right, the "bytes output" counters are indeed interface specific.

 

Unfortunately for ingress qos policies (service-policy input) there is no such "bytes" counter in the output of command "show policy-map interface", there you only get the "packets" counter which has the problem I described earlier.

So this "bytes" counter is only available for egress qos policies (service-policy output).

 

Nevertheless, egress is nice too.

 

Do you happen to know what the SNMP OID is for retrieving this "bytes output" counter?

I tried these OIDs but without success:

- cbQosCMPostPolicyByte64 ( .1.3.6.1.4.1.9.9.166.1.15.1.1.10) : non zero values but they are quite different from the "bytes output" values in the CLI.

-  cbQosCMPrePolicyByte64 ( .1.3.6.1.4.1.9.9.166.1.15.1.1.6): all zero values. 

Participant

Re: QoS on Catalyst 3850: are class-map statistics really per interface? (show policy-map interface)

Hi

 

no, i ve never worked with specific oid s considering the 3850 switch, only with wifi controllers

 

Maybe just shoot a new question in this forum to where to find those. 

There must be someone who knows ;-)

 

Re: QoS on Catalyst 3850: are class-map statistics really per interface? (show policy-map interface)

OK I will do that!


One more question regarding the "packets" counters:

I just noticed that the described problem only seems to apply to interfaces which are part of a port-channel:
- interfaces Te1/0/1 to Te1/0/8 (each one is part of a different port-channel, as described in initial question) all have the same counters, see below.
- interfaces Te1/0/9, Te1/0/10, Te1/0/12 (not part of a port-channel) do seem to have interface specific counters, see below.

 

So the problem must be related to the port-channels.

 

Do you see the same on your switches?

 

Interfaces in a port-channel:
hostname#show policy-map interface te1/0/1 (snippet)
629119151 packets
558116559 packets
26918031513 packets
hostname#show policy-map interface te1/0/2 (snippet)
629119969 packets
558117874 packets
26918073331 packets
hostname#show policy-map interface te1/0/3 (snippet)
629119969 packets
558117874 packets
26918073331 packets

 

Interfaces not in a port-channel:
hostname#show policy-map interface te1/0/10 (snippet)
440198 packets
220924 packets
7942384 packets
hostname#show policy-map interface te1/0/12 (snippet)
5263648 packets
4718536 packets
83595286 packets

Participant

Re: QoS on Catalyst 3850: are class-map statistics really per interface? (show policy-map interface)

Hi

 

well i have a different qos policy for the uplinks which are in a port-channel. 

 

And getting confused :-)

 

OK

Port-channel 100 has 2 members: Gi 1/1/1, Gi 2/1/1

 

show policy-map int Gi 1/1/1

 

Class-map: CM_VOIP (match-any)
30012737 packets
Match: dscp ef (46)
0 packets, 0 bytes
5 minute rate 0 bps

 

show policy-map int Gi 2/1/1

Class-map: CM_VOIP (match-any)
21963289 packets
Match: dscp ef (46)
0 packets, 0 bytes
5 minute rate 0 bps

 

Packet count differs here on the members of the Port-channel. Due to the load balancing algo of a port channel i think. 

 

Now the access-links

 

sh policy-map int Gi 1/0/1


Class-map: CM_VOIP (match-any)
21170853 packets
Match: dscp ef (46)
0 packets, 0 bytes

 

sh policy-map int Gi 1/0/2

Class-map: CM_VOIP (match-any)
21170853 packets
Match: dscp ef (46)
0 packets, 0 bytes
5 minute rate 0 bps

 

Same amount of packets. Overhere it s the other way around, interfaces which are not in a port-channel have the same amount of packets, of which i said earlier i think are cumulative of all 48 interfaces. 

Members of port-channels have different counts, i think due to load balancing. 

 

 

What about switch 2

 

show policy-map int 2/0/1 

Class-map: CM_VOIP (match-any)
15183569 packets

switch 2 (interface 2/0/1) has different counters, so i think its cumulative on a per switch base. 

 

 

 

 

Participant

Re: QoS on Catalyst 3850: are class-map statistics really per interface? (show policy-map interface)

Hi

 

my last post seem to have disappeared here. 

 

i post this again short: 

 

What i see: 

 

interfaces / members of a port channel here have different counts, i think because of load balancing algo on a port-channel

 

interfaces which are not in a channel all have the same counts on a per switch base in a stack

 

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