QoS trust dscp in IOS XE

[ben.epskamp]

On the Cisco WS-3560V2-48TS-E (IOS Version 12.2(50)SE3) Switches we used “Conditional Trust” in our QoS marking based on the “trust dscp” IOS CLI command as shown in the next IOS CLI configuration segment.

ip access-list extended CLASSIFY_MARKED

 deny   ip any any dscp default

 permit ip any any

ip access-list extended CLASSIFY_MANAGEMENT

 permit ip ---

-----

class-map match-all ALLREADY_MARKED
 match access-group name CLASSIFY_MARKED

class-map match-all CLASS_MANAGEMENT
 match access-group name CLASSIFY_MANAGEMENT

----

policy-map MARK_INGRESS

 class ALLREADY_MARKED

  trust dscp

class CLASS_MANAGEMENT
  set dscp cs3
---

interface FastEthernet0/1

  service-policy input MARK_INGRESS

The above IOS CLI command segment leaf all dscp marked incoming frames (dscp <> 0) untouched and all not dscp marked incoming frames (dscp = 0) are marked according a configured scheme (not fully show in the above IOS CLI command segment).

The form Cisco recommended successor the WS-C3560-48TS-E (IOS XE Version 03.03.04SE) doesn’t support the “trust dscp” IOS CLI command anymore.

Does anybody know a way to configure the same functionality in IOS XE.

[Madhukrishnan Gopinathan Nair]

Hi,

I guess trust dscp is on by default.

Hope this helps.

Thanks,

Madhu

[ben.epskamp]

Thanks you for your response.

Yes you’re right there, but the problem is that if an incoming packed has a dscp value 0 (not marked) than it should be remarked and only then. Therefore I need the trust dscp command as shown in the IOS CLI configuration segment I posted, otherwise the incoming packed is remarked no matter what dscp value it has. I didn’t find another way yet to solve this without the trust dscp command.