Policy-map counters not increasing for QOS

[rick505d3]

Hi,

I am doing a lab test to verify QOS on a Cisco 2960s 49P switch. The service policy applied to the interface Gi1/0/1 seems to be working as Wireshark capture (on the uplink trunk ports) indicate all traffic is correctly marked ("ef" for testint purposes). However, none of the counters in "show policy-map int gi1/0/1" seems to be increasing.

Standard IP access list acl-01
    10 permit any
Class Map match-all cm-01 (id 4)
   Match access-group name acl-01
  Policy Map pm-01
    Class cm-01
      set dscp ef
interface GigabitEthernet1/0/1
switchport access vlan 240
switchport mode access
switchport voice vlan 234
spanning-tree portfast
service-policy input pm-01
#show policy-map  interface gi1/0/1
GigabitEthernet1/0/1
  Service-policy input: pm-01
    Class-map: cm-01 (match-all)
      0 packets, 0 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: access-group name acl-01
    Class-map: class-default (match-any)
      0 packets, 0 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: any
        0 packets, 0 bytes
        5 minute rate 0 bps
#show mls qos
QoS is enabled
QoS ip packet dscp rewrite is enabled
#show mls qos  interface gi1/0/1
GigabitEthernet1/0/1
Attached policy-map for Ingress: pm-01
trust state: not trusted
trust mode: not trusted
trust enabled flag: ena
COS override: dis
default COS: 0
DSCP Mutation Map: Default DSCP Mutation Map
Trust device: none
qos mode: port-based
#show ver
Switch Ports Model              SW Version            SW Image
------ ----- -----              ----------            ----------
*    1 52    WS-C2960S-48LPS-L  15.0(2)SE2            C2960S-UNIVERSALK9-M

Has anyone else observed this ? A bug ?

Regards,

Rick.

[Peter Paluch · Accepted solution]

Hi Rick,

I believe this is normal behavior. On switches, many operations including QoS marking manipulation is performed in hardware while the show policy-map command shows you the software counters associated with the policy-map. As the hardware does not report back the number of packets handled by the policy-map (which could be quite intensive as these operations are performed at wire rate), the counters in the policy-map are not incremented. The same goes, for example, for ACLs - the counters displayed by individual ACL entries do not increase, either.

If you check out the command reference for this command at:

http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/15.0_2_se/command/reference/cli2.html#wp1948343

the documentation says: Though visible in the command-line help string, the control-plane and interface keywords are not supported, and the statistics shown in the display should be ignored.

Best regards,

Peter

[rick505d3]

Thanks Peter. That explains the behaviour.

Regards,

Rick.