DSCP marking through a Cisco router

acharreau used Ask the Experts™
Hi Experts,

I need to set up QOS based on DSCP field through a Cisco Router.

I have got a Cisco LAN and phones marking DSCP fields as CS3 for sig and EF for voice.
I need to keep these marks crossing a Cisco router (2901) that is default GW for the site and also from the WAN to the LAN.

For example :

If a phone marks EF in a packet and this packet is forwarded from inside to outside interface of the router, I need to keep it marked EF.

If a packets comes from the WAN with a DSCP EF, I would like to keep it on the LAN.

I tried commands below but not working.
Any idea will be appreciated.

Best regards,

class-map match-all VOIP_DATA
 match ip dscp ef

policy-map PM
 class VOIP_DATA
  set dscp ef

interface GigabitEthernet0/0
 description OUTSIDE
 service-policy input PM
 service-policy output PM

interface GigabitEthernet0/1.210
 description INSIDE VOIP
 service-policy input PM
 service-policy output PM
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Don JohnstonInstructor
Top Expert 2015
Did you trust the interface?

mls qos trust
step 1) put  mls qos on Switch
step 2) put int f0/0
          # mls qos trust device    this will be on switch.
step3) On router do input remarking on interface connecting switch
           for eg
            class-map match-any RTP
 description [ VOIP Audio & Control ]
 match protocol rtp audio
 match protocol rtcp
or match cos {value}

policy-map QOS-IN
 class RTP
  set ip dscp ef

int f0/0
service-policy input QOS-IN

please sh mls qos int f0/0  statistics --lan interface ...run on switch
for WAN better be sure ISP sends the proper marking ..
because normally ISP uses its own marking ...

also on lan switch  u try
 int f0/0
mls qos trust cos
Istvan KalmarHead of IT Security Division
Top Expert 2010

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