QoS Basics Question

[mkazam001]

I would like to apply QoS to VoiP traffic for Avaya phones on our work network. There are a number of really old switches (some wont even have QoS capapbility) but we also have an ASA. I know how to configure QoS on the ASA.

My question is, will the VoiP packets even have the DSCP EF value by the time they get to the ASA, as there is no QoS configured on the switches - or will the DSCP value be 0 & hence traffic treated as BE as there are no CoS-to-DSCP mappings?

If that is the case, then I would have to consider prioritisation of VoiP traffic 'only on the ASA' based on source IP range & ACL.

Regards,

Azam

[Chris Deren]

If there is no QoS enabled on the switch then the QoS markings should be preserved across the switch.

[mkazam001]

Hi Chris,

I thought that a switch interface had to be configured with (eg.) auto qos voip trust to trust the markings from the IP phone?

[Chris Deren]

It does if you have QoS enabled globally on the switch, if no QoS is enabled then all markings are preserved onto the next hop.

[mkazam001]

I understand now, thank you!

I'm sure I'll be back for further questions as I work my through the Cisco QoS book :)

Regards,

Azam

[Ashish Patel]

Span the incoming and or the uplink port and you can check for sure. Rgs ashish