I have a network with Cisco switches, Cisco IP Phones and video traffic. I want to add QoS markers to my traffic but I don't want to do it manually.

Ideally I want to use Cisco's auto QOS features but I'm not sure where I should add the commands.

My IP phones are on access switches and the traffic goes back to my core switch where it is routed towards several call manager servers.

My understanding is to do this :

  • Enable QoS on all switches (access, distribution & core) with "mls qos"
  • Enable auto QOS markings on interfaces connected to cisco ip phones with "auto qos voip cisco-phone"
  • Enable auto QOS trust on network uplinks with "auto qos voip trust"

Is this right ? Is there anything else to do ? Should I put "auto qos voip trust" on network uplinks for both directions on traffic ? (forward and back) Will there be downtime to be aware of ?

Thanks Jeremy

1 Answer 1


For Cisco IP phones, you've definitely got the right configuration:

mls qos
interface UPLINK
 ! Unconditionally trust all QoS markings
 auto qos voip trust
interface ACCESS
 ! Look for the Cisco Phone's CDP frames, and trust VoIP from the phone...
 auto qos voip cisco-phone

Should I put "auto qos voip trust" on network uplinks for both directions on traffic?

Yes, auto qos voip trust is required on both sides of any uplink for end-to-end QoS functionality (which is what you'd want, of course).

Will there be downtime to be aware of?

There is no downtime associated with QoS settings. I have enabled qos (platform-wide, and on individual links) with no observable impact; even on links that were heavily utilized, there was no perceivable downtime for transit traffic.

For more info, you can reference Cisco's Auto QoS Whitepaper


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