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COS REWRITE RULE question on MX5

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  • 1.  COS REWRITE RULE question on MX5

    Posted 07-19-2017 09:45

    Hi everybody,

    Please consider the following example on “REWRITE RULE” on MX5.



    On g0/1/0.0, we have a classifier JEE which places all traffic with DSCP code points: 010101, 010111 into egress forwarding class CRITICAL on g0/2/0.0:

    class-of-service {

       classifiers {

           dscp JEE

                         forwarding-class CRITICAL {

                   loss-priority high code-points 010111;

                   loss-priority low code-points 010101;


    On egress port 0/2/0.0, we have a re write rule JOO that remarks DSCP value on all traffic in egress forwarding class CRITICAL on g0/2/0.0

    rewrite-rules {

           dscp JOO

                   forwarding-class CRITICAL {

                   loss-priority low code-point 010101;

                   loss-priority high code-point 010111;


    Let say a packet with DSCP 010111 arrives on g0/1/0.0, our router classifies it  based on classifier JEE,  and places it into FORWARDING CLASS CRITICAL on egress interface g0/2/0.0

    Since g0/2/0.0 has a REWRITE RULE JOO, router has to remark the DSCP value with either 010101 or 010111, question is which value will be used for remarking DSCP 010111 or 010111?

    Much appreciated!!

  • 2.  RE: COS REWRITE RULE question on MX5
    Best Answer

    Posted 07-19-2017 11:05



    From the JEE BA classifier, dscp 010111 is assigned to FC CRITICAL with packet loss-priority [plp] high.

    JOO re-write rule will dscp re-mark packets in FC CRITICAL as below:


    plp=high, dscp re-write: 010111

    plp=low, dscp re-write: 010101


    Hope this helps.