Default QOS Trust behaviour

[Redmist]

Hi,

I've just been testing QOS on 3560 with version 15.0(1) and it seems the the default qos trust behavior on access ports has changed. By default the trust state of a port is not to trust anything, however rather than rewriting the DSCP value of the incoming packets and settign it to 0 the switch now seems to leave the DSCP value unchanged.

SW04-C3560(config)# do sh mls qos int g0/2

GigabitEthernet0/2

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

SW01-C3550(config-if)#do sh mls qos int f0/13

FastEthernet0/13

trust state: not trusted

trust mode: not trusted

COS override: dis

default COS: 0

DSCP Mutation Map: Default DSCP Mutation Map

I tested this by tagging the inbound packets with DSCP 40 and when I recieved them on my PC they were unchanged.

Repeated the same test on the old 3550's with version 12.2.25 and the packets arrive with DSCP reset to 0.

Just wondering if anybody else had come across this?

[Joseph W. Doherty]

Disclaimer

The     Author of this posting offers the information contained within this     posting without consideration and with the reader's understanding  that    there's no implied or expressed suitability or fitness for any   purpose.   Information provided is for informational purposes only and   should not   be construed as rendering professional advice of any kind.   Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In     no event shall Author be liable for any damages whatsoever   (including,   without limitation, damages for loss of use, data or   profit) arising  out  of the use or inability to use the posting's   information even if  Author  has been advised of the possibility of  such  damage.

Posting

What the global status of QoS on both switches?  Often if global QoS is disabled, switch will not reset QoS markings.  If global QoS enabled, switch will reset QoS markings unless configured not too.

[Redmist]

Hi,

QOS is enabled globally and there's no trust or service policies applied to the interfaces. Just straightforward access ports.

[Joseph W. Doherty · Accepted solution]

Disclaimer

The      Author of this posting offers the information contained within this      posting without consideration and with the reader's understanding   that    there's no implied or expressed suitability or fitness for any    purpose.   Information provided is for informational purposes only  and   should not   be construed as rendering professional advice of any  kind.   Usage of  this  posting's information is solely at reader's own  risk.

Liability Disclaimer

In      no event shall Author be liable for any damages whatsoever    (including,   without limitation, damages for loss of use, data or    profit) arising  out  of the use or inability to use the posting's    information even if  Author  has been advised of the possibility of   such  damage.

Posting

Does the 3560 have "no mls qos rewrite ip dscp" (global command)?

[Redmist]

Cheers Joseph

Couldn't see for looking