QOS marking question.

[davidkinsler]

Hello,

     I have a question on marking traffic.  I need to know if there is a way to 'trust' the markings from certain networks or hosts, while resetting markings on all other traffic.  Here is what I am trying to do..

     Access list 190 defines hosts that would be communicating and are to be 'trusted'.  I want to trust their markings, but all other traffic gets reset to default.  Im hoping by leaving the class cmap_VOICETRAFFIC empty, with out a corresponding 'set' statement, that keeps it from falling into class-default.  Can anyone shed some light on this please?

class-map match-all dscp-ef
match ip dscp ef
class-map match-any cmap_VOICETRAFFIC
match access-group 190

policy-map pmap_VOICETRAFFIC
class cmap_VOICETRAFFIC
class class-default
  set dscp default
policy-map queue-on-dscp
class dscp-ef
  priority 3880
class class-default
  fair-queue
  random-detect dscp-based

[Collin Clark]

Just to make sure I have this clear; you want 'trusted' end points to retain their DSCP values. Any other system you want the DSCP values cleared/set to 0. Also you want no traffic to fall into the default class. Is this correct?

[davidkinsler]

Sort of.  I want trusted traffic to retain its dscp markings and ALL other traffic to

be reset.  I was under the impression having the class-default would mark everything that was not already trusted down to default, which was 0.

[Collin Clark]

The default class will not remark the DSCP values. I would think the easiest way would be to add another class map and set the DSCP value to 0. Check the QoS SRND, it's a great reference.

http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoSDesign.html#wp999115

[davidkinsler]

The book from cisco i have says "If a packet is examinded by a policy map and it does not match any

of the explicitly defined classes, the packet is considered to match class-default."  Page 152 of the qos exam study guide.  And in the book, they are using "set dscp BE" in class-default.  So your telling me it doesnt actually do this?