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Hi,

I have a customer configured on my PE as follows:

interface Serial5/0:0

 ip vrf forwarding V5375:Customer_A

 ip address 10.70.28.165 255.255.255.252

 no cdp enable

 service-policy input Customer_A_In

end

PE-2#sh policy-map Customer_A_In

  Policy Map Customer_A_In

    Class Customer_A_GOLD

     police cir 384000 bc 72000 be 144000

       conform-action set-mpls-exp-transmit 5

       exceed-action drop

       violate-action drop

    Class class-default

     police cir 128000 bc 24000 be 48000

       conform-action set-mpls-exp-transmit 4

       exceed-action drop

       violate-action drop

PE-2#sh class-map Customer_A_GOLD

 Class Map match-any Customer_A_GOLD (id 15)

   Match access-group name Customer_A_GOLD

PE-2#sh access-lists Customer_A_GOLD

Extended IP access list Customer_A_GOLD

    10 permit ip host 192.168.70.10 any (4003642 matches)

PE-2#

I just noticed something.  When actually going to the policy-map and looking at the options for conform-action, I get the following:

R1(config-pmap-c-police)#conform-action ?
  drop                                                drop packet
  set-clp-transmit                              set atm clp and send it
  set-dscp-transmit                           set dscp and send it
  set-mpls-exp-imposition-transmit  set exp at tag imposition and send it
  set-prec-transmit                           rewrite packet precedence and send it
  set-qos-transmit                             set qos-group and send it
  transmit                                          transmit packet

However, in the config, the "set-mpls-exp-imposition-transmit" shows up as:

conform-action set-mpls-exp-transmit 5

So, I imagine what is happening is that the exp bit is being set on the label as it is placed on top (imposed) of the packet.

1) You will set the Exp bit to 5 once a label has been put on the packet. I do beleive that it will be overwriting the IP Prec fields with the Exp 5. So if the customer is using DSCP you will have altered the packet QoS

2) As always this is being done by CEF.

 The imposition on the top most label will leave the original QoS fields of the packet untouched.

Hi,

I am of the impression that the EXP bit can be set only if MPLS header is present in the packet. Since the customer is not using MPLS and the set-mpls-exp-transmit is used in an interface which is not mpls enabled. PE is MPLS enabled, but that interface is not.

Please correct me if I am wrong.

Hi blankdot,

The way I see it is that any remote routes in the vrf cef table for V5375:Customer_A will have a NH address of a VPNV4 peer router (probably the egress PE). Now you have an MPLS enabled core (PE to P to PE), so when your ingress router does a NH lookup for any packets received from the vrf interface Se5/0:0, it finds that it has a LSP/outgoing Label for the next hop address and the label(s) will be imposed before the packets get transmitted.

So I think the set-mpls-exp-transmit command in this situation will not have the desired effect if applied IN on a non-mpls customer interface. You would have to mark the packets via another method IN and then remark before transmit to the MPLS core.

What do you think?