Set DSCP default

Gents,

i have this config and i am trying to FIND confirmation on the cisco web-site of what this does

Class class-default

set dscp default  - this is the line i am interested in ...the setting of DSCP back to default

according tot he QOS mapping tables , the default is 0000 , but i cannot find confirmation that this is how Cisco have implemented this.

i have tried runnign on this on various platforms and various IOS`s , but i get inconsistant results.( e.g Sup720 with 12.2-33SXI train the incoming marking is not set to 0000)

Does anyone know of a Link on the CCO where this information is held ?

many thanks

Comments

  • according tot he QOS mapping tables , the default is 0000 , but i cannot find confirmation that this is how Cisco have implemented this.

    Indeed, DSCP default is DSCP with value 000 000. See this page from Cisco:
    http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a00800949f2.shtml

  • I've always seen default marked to 0. What is your sup720 marking it to exactly?

  • Check this RFC 2474 out, written by Cisco folks.
    See section 4.1 A Default PHB.
    http://tools.ietf.org/html/rfc2474

  • Hi secondsight,

    The default DSCP is 000 000.

    Yes you can refer this URL:

    http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a00800949f2.shtml

    and see my example about set DSCP default:

    Topology: R1-R2-R3

    R1(config)#policy-map TEST

    R1(config-pmap)#class class-default

    R1(config-pmap-c)#set dscp EF

    R1(config-pmap-c)#exit

    R1(config-pmap)#int s0/0

    R1(config-if)#service-policy out TEST

    !

    R2(config-if)#do show run | in access-list

    access-list 100 permit ip any any dscp af11

    access-list 100 permit ip any any dscp af12

    access-list 100 permit ip any any dscp af13

    access-list 100 permit ip any any dscp af21

    access-list 100 permit ip any any dscp af22

    access-list 100 permit ip any any dscp af23

    access-list 100 permit ip any any dscp af33

    access-list 100 permit ip any any dscp af31

    access-list 100 permit ip any any dscp af32

    access-list 100 permit ip any any dscp af43

    access-list 100 permit ip any any dscp af42

    access-list 100 permit ip any any dscp af41

    access-list 100 permit ip any any dscp ef

    access-list 100 permit ip any any dscp default

    !

    R2#show access-lists

    Extended IP access list 100

        10 permit ip any any dscp af11

        20 permit ip any any dscp af12

        30 permit ip any any dscp af13

        40 permit ip any any dscp af21

        50 permit ip any any dscp af22

        60 permit ip any any dscp af23

        70 permit ip any any dscp af33

        80 permit ip any any dscp af31

        90 permit ip any any dscp af32

        100 permit ip any any dscp af43

        110 permit ip any any dscp af42

        120 permit ip any any dscp af41

        130 permit ip any any dscp ef (19 matches) All packets marked EF coming from R1

        140 permit ip any any dscp default

    !

    R2(config)#class-map TEST

    R2(config-cmap)#match dsc

    R2(config-cmap)#match dscp EF

    R2(config-cmap)#exit

    R2(config)#policy-map TEST

    R2(config-pmap)#class TEST

    R2(config-pmap-c)#set dscp default

    R2(config-pmap-c)#class class-default

    R2(config-pmap-c)#set dscp af22

    R2(config-pmap-c)#exit

    R2(config-pmap)#int s0/1

    R2(config-if)#service-policy output TEST : R2 changing DSCP EF value to default and af22 for rest.

    !

    R3(config)#access-list 100 permit ip any any dscp af11

    R3(config)#access-list 100 permit ip any any dscp af12

    R3(config)#access-list 100 permit ip any any dscp af13

    R3(config)#access-list 100 permit ip any any dscp af21

    R3(config)#access-list 100 permit ip any any dscp af22

    R3(config)#access-list 100 permit ip any any dscp af23

    R3(config)#access-list 100 permit ip any any dscp af33

    R3(config)#access-list 100 permit ip any any dscp af31

    R3(config)#access-list 100 permit ip any any dscp af32

    R3(config)#access-list 100 permit ip any any dscp af43

    R3(config)#access-list 100 permit ip any any dscp af42

    R3(config)#access-list 100 permit ip any any dscp af41

    R3(config)#access-list 100 permit ip any any dscp ef

    R3(config)#access-list 100 permit ip any any dscp default

    R3(config)#int s0/0

    R3(config-if)#ip access-group 100 in

    R3#show access-lists

    Extended IP access list 100

        10 permit ip any any dscp af11

        20 permit ip any any dscp af12

        30 permit ip any any dscp af13

        40 permit ip any any dscp af21

        50 permit ip any any dscp af22 (6 matches)

        60 permit ip any any dscp af23

        70 permit ip any any dscp af33

        80 permit ip any any dscp af31

        90 permit ip any any dscp af32

        100 permit ip any any dscp af43

        110 permit ip any any dscp af42

        120 permit ip any any dscp af41

        130 permit ip any any dscp ef

        140 permit ip any any dscp default (30 matches)


    R1#ping 3.3.3.3 so lo0

    Type escape sequence to abort.

    Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:

    Packet sent with a source address of 1.1.1.1

    !!!!!

    Success rate is 100 percent (5/5), round-trip min/avg/max = 28/65/120 ms

    !


    R2#show access-lists

    Extended IP access list 100

        10 permit ip any any dscp af11

        20 permit ip any any dscp af12

        30 permit ip any any dscp af13

        40 permit ip any any dscp af21

        50 permit ip any any dscp af22

        60 permit ip any any dscp af23

        70 permit ip any any dscp af33

        80 permit ip any any dscp af31

        90 permit ip any any dscp af32

        100 permit ip any any dscp af43

        110 permit ip any any dscp af42

        120 permit ip any any dscp af41

        130 permit ip any any dscp ef (78 matches)

        140 permit ip any any dscp default

    !


    R3#show access-lists

    Extended IP access list 100

        10 permit ip any any dscp af11

        20 permit ip any any dscp af12

        30 permit ip any any dscp af13

        40 permit ip any any dscp af21

        50 permit ip any any dscp af22 (60 matches)

        60 permit ip any any dscp af23

        70 permit ip any any dscp af33

        80 permit ip any any dscp af31

        90 permit ip any any dscp af32

        100 permit ip any any dscp af43

        110 permit ip any any dscp af42

        120 permit ip any any dscp af41

        130 permit ip any any dscp ef

        140 permit ip any any dscp default (45 matches)


    Any queries are welcome!



    HAPPY STUDY

    [:D]


     

  • Hi , its not stripping the DSCP value , whatever the dscp value was set by the device , ( video or phone) i am seeing leaving the switch ..

    it might just be me ...i just wanted to check i am not going mental ..[:D]

  • thanks for your responses guys ,,, cheers nnn

  • Steve Jobs said "Stay Hungry, Stay Foolish" [;)]

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