Pre classification with ADSL Dialer interface

Unanswered Question
Aug 29th, 2009


Can some please help me figure out why i can't pre classify traffic correctly?

Here is what i'm trying to do - I have an ADSL home office router with an IP phone connected to a 3560 switch of interface Fa0/0. If i enable nbar an match traffic on the protcol type rtp and remark to EF this seems to work fine. However when i try to match traffic before goig to the dialer interface i never see it being marked as EF or even matching RTP. This is confusing me as I have ESP wrapping around the GRE tunnel and therefore i thought i should have pre classify on the tunnel interface, so before the traffic gets wrapped in a GRE it should create a copy of mark the DSCP as EF. Please have a look at my config and see if anyone has an idea.

Help rated.



I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
Edison Ortiz Sat, 08/29/2009 - 06:33

You should classify traffic at ingress on the router. Your service-policy on F0/0 is for egress thus you are classifying RTP traffic from the router to the phone, not from the phone to the router.

You also have an incorrect service-policy under the dialer1 interface as it is marking on egress. The only way to see the QoS marking is to verify the packet at the remote router.

Ideally, you mark on ingress - send the packet to the tunnel via the static route and the tunnel will copy the TOS value from the IP Header to the GRE Header.




gavin.mckee Sat, 08/29/2009 - 07:55

Hi Edison,

Thanks for your reply, can i ask you for some advice on this scenario:

I want to make sure that i apply EF and AF41 markings to RTP and SKINNY traffic, i'm using NBAR to match these, i need these markings to be carried into my HQ network but i also need to make sure that when congestion occurs outbound on the dialer interface that this traffic gets priority, thus i was thinking i need to pre classify the traffic as the payload ultimaley gets carried inside a gre and esp header.

Can you suggest a template relative to my configuration that would help.

I think this would help me understand the logic behind the process.

Thanks for your help.


Edison Ortiz Sat, 08/29/2009 - 09:23

class-map match-all SIGNALING

match protocol skinny

class-map match-all VOICE-Fa0/0

match protocol rtp

policy-map INSIDE-Fa0/0

class VOICE-Fa0/0

set ip dscp ef


set ip dscp af41

interface FastEthernet0/0

service-policy input INSIDE-Fa0/0

class-map match-any Priority-Traffic

match ip dscp ef

match ip dscp af41

policy-map Tunnel-QoS

class Priority-Traffic

priority xxx

interface Tunnel217

qos pre-classify

interface dialer1

service-policy output Tunnel-QoS


This Discussion