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enter image description hereI've written the below config for the following network topology:

6509 switch acting as collapsed core for data access switches, voice access switches and wifi access switches. The 6509 then connects to a cisco edge router which then connects to the ISP MPLS network.

I want to first mark voice packets coming from the access switch, then prioritise them as they pass through the 6509 up to the router and then prioritise them once more while they pass through the router and onto the mpls network.

Will my code work?

Marking the voice packets on the core switch:

class-map match-all Mark_Voice  
 match access-group 107  
!  
policy-map MARK_VOIP  
 class Mark_Voice  
  set ip dscp ef  
!  
int port-channel 2  
service-policy input MARK_VOIP  

Then on the router facing interface of the core switch I want to prioritise VOICE packets:

class-map match-all SWITCH_to_ROUTER_Voice  
 match  dscp ef  
!  
policy-map Voice  
 class SWITCH_to_ROUTER_Voice  
    priority 6200  
  set ip dscp ef  
 class class-default  
    fair-queue  
     random-detect  
!  
int gi 1/1/1:  
service-policy output Voice  

Finally when the voice packets get to the WAN interface of the Router, prioritise again:

class-map match-all MPLS_Voice  
 match  dscp ef  
!  
policy-map MPLS_Voice  
 class MPLS_Voice  
    priority 6200  
  set ip dscp ef  
 class class-default  
    fair-queue  
     random-detect  
!  
int gi 0/0/0:  
service-policy output MPLS_Voice  
  • 1
    I don't think you want to use fair-queue and random-detect with VoIP. I think you probably want to assign to a priority queue with a guaranteed bandwidth or percent. Random detect is only useful for TCP segments where losing some will slow down the TCP flow. You are completely forgetting that the 6509 is a switch, and you are not setting up the layer-2 QoS on it. – Ron Maupin Jul 13 '15 at 23:22
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    Is the router to your ISP only used for VoiP traffic ? I would suggest adding a simple drawing showing the ports and where they connect. What is the speed of the MPLS ? Number of voice calls ? Do you have any agreement with ISP to handle dscp ef traffic differently ? – Pieter Jul 14 '15 at 7:12
  • Hi guys,thanks for commenting. I've added a diagram to help explain. – Tullio_IRL Jul 14 '15 at 17:23
  • The connection between the 6509 and the router is layer 3, it will be passing voip and data traffic. The connection from the 6509 to the voice switch is layer 2. – Tullio_IRL Jul 14 '15 at 17:24
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    For the 6509, you need to determine the layer-2 QoS capabilities of the line cards (1p3q8t, 1p3q4t, 1p2q2t, etc.) and be sure to configure that correctly. I would mark the traffic on the access switches and just trust it on the 6509. The router will trust what the 6509 gives it, so you should just need to queue on the router, not mark it again. Mark once, as close to the source as possible. In fact, the phones may already mark the VoIP traffic, and the access switches can just trust that. – Ron Maupin Jul 14 '15 at 18:14

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