6500 VSS policy-maps and classification

Unanswered Question
Jun 28th, 2010

Hello group,

Another QoS related question, this time it deals with a 6500 running VSS with IOS 12.2(33)SXI3. I have a policy map that is applied to a physical interface that is looking for UDP video traffic and marking it as AF41. After applying the service-policy to the physical interface I look at the policy-map and I see matches on the interface like it is marking, but a sniff tells me otherwise. This is the almost the exact opposite of the 3750 problem that I was seeing in this bug report: http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCec08205

I have been doing some reading and I know that VSS does QoS differently across the VSL (i.e. COS only, unchangeable COS to DSCP mappings) but does that matter on physical ethernet ports for servers and uplinks to other switches?

Below is the config from the VSS switch. For the record I have tried QoS on the VLAN as well and no such luck.

ip access-list extended SXDMSWMS1-Multicast
permit udp host any eq 25385
permit udp host any eq 30657
ip access-list extended SXDMSWMS2-Multicast
permit udp host any eq 25385
permit udp host any eq 30657


class-map match-any SXDMSWMS-Multicast-cmap
  match access-group name SXDMSWMS1-Multicast
  match access-group name SXDMSWMS2-Multicast

policy-map QoS-Policy-Cisco-DMS
  class SXDMSWMS-Multicast-cmap
   set dscp af41


interface GigabitEthernet1/1/31
description SXDMSWMS2
switchport access vlan 3098
switchport mode access
mls qos trust dscp
spanning-tree portfast edge
service-policy input QoS-Policy-Cisco-DMS

Hopefully someone can tell me where I'm going wrong.

Thank you,

AJ Schroeder

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
belovell Thu, 07/01/2010 - 17:49

mls qos trust dscp

I don't think you are allow to do this and manually rewrite QoS values. It's either or.


AJ Schroeder Fri, 07/02/2010 - 11:05

I thought I read that at some point, but I was under the impression that it only applied to PFC2 and below.

I will try your suggestion and get back to you.

Thank you,


belovell Wed, 07/07/2010 - 11:38

Just to double check make sure you try removing and adding the policy back once "mls qos trust dscp" was removed. They might have gotten into an argument with each other as the "trust" command sets a bit in our internal header that precludes remarking policies.

If your packet captures show that the traffic is *still* not being marked then I think you need to open a case with the TAC to look into this as the next step would be along the lines of ELAM and other things that are not documented externally.


AJ Schroeder Thu, 07/22/2010 - 07:39

Does the command "mls qos 10g-only" command have anything to with the VSS not marking traffic on a non 10GE port? I have noticed this command in the global configuration on the switch, would that be ignoring the marking?



This Discussion