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QoS on SUP720-3B


I know there's quite a few posts on here about what you can and can't do with QoS on a SUP720 but we have a QoS template that I need to deploy (or advise on reconfiguration) for a customer that uses the Priorty command for Voice in the policy.

Taffic is marked at the Access layer in this network so the WAN router just looks at the DSCP markings and the policy just acts on them on the router WAN interface.  This is fine when we use traditional WAN routers but in this case we've been asked to use 6500's with SUP720's and the Priority and Bandwidth commands are not supported outbound on the SUP720 gig interfaces.

Can anyone offer some advice on a workaround as we need to Voice placed in the Priority queue and ensure it's policed up to the same CAR as we subscribe to off the carrier at their PE router (in this case 30Mb).?

Here's my QoS policy and interface config.  Would appreciated any help.  Thanks.....John

policy-map ABC
  class VOICE
    priority 30000
  class AF4x
    bandwidth remaining percent 1
  class AF3x
    bandwidth remaining percent 15
    random-detect dscp-based
  class AF2x
    bandwidth remaining percent 45
    random-detect dscp-based
  class AF1x
    bandwidth remaining percent 5
    random-detect dscp-based
  class class-default
    bandwidth remaining percent 34
    random-detect dscp-based

interface GigabitEthernet5/1
bandwidth 510000
no ip address
speed nonegotiate

interface GigabitEthernet5/1.34
description WAN Circuit
encapsulation dot1Q 34
ip address
service-policy output ABC  (switch replies with‘'priority command is not supported in output direction for this interface’)

Cisco Employee

Re: QoS on SUP720-3B

Hi John,

Looks like you are doing 300M subrate off the 1GE interface. Your best bet is to use the SIP/SPA with HQoS so you can shape the interface to 300M and apply MQC.



Hall of Fame Super Silver

Re: QoS on SUP720-3B

Hello John,

you need to use PFC based QoS that uses QoS tools of multilayer switches

in short:

you need to trust DSCP settings on port that receives traffic, an internal DSCP tag = received DSCP values is set.

Then you need to map  internal DSCP values to output queues

You can tune some parameters of the queues ( thresholds for Weighted Round Robin)

The output queues, but also the input queue depends from module type.


Again depending on the module a priority queue can exist and you can map to it the DSCP value of VOIP RTP packets.

Hope to help


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