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Allison_Burgers
Beginner

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).

6 REPLIES 6
Ton V Engelen
Participant

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. 

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. 

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 ;-)

 

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

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. 

 

 

 

 

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