change the default CoS 5 for voip

Unanswered Question
Jun 15th, 2007

hi i was looking for a way to change the cos 5 for an Ipphone to 6 , which is connected with a pc to the secondary port and keep the cos 3 for the pc frames. the switch its a 3548XL.

thanks

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Chris Deren Fri, 06/15/2007 - 05:49

You should never change it to COS as that is used by routing protocols, and typically does not have higher priority. With QoS you can prioritize any traffic you want and it's not really dependant on the COS value. How do you figure the PC is using COS 3, are you overrriting it on the NIC card?

Here is my recommandation based on Cisco best practices: Leave RTP traffic at 5, voice signialing at 3, all best effort traffic at 0.

Alos, I dont belive 3548 can do much LAN QoS anyhow...

Good reading is QoS SRND at:

www.cisco.com/go/srnd

HTH, please rate all posts!

Chris

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