Question about COS and QOS on 3524

Unanswered Question
Jun 20th, 2007

If I understand it correctly on a switch port that has an IP phone plugged into it the command "switchport priority extend cos 0" would ensure that the PC traffic was set to COS 0.

But what if this command was applied to my layer 2 WAN interface? Would all traffic (including voice) be re-mapped to COS 0? That?s the way my WAN interface is currently configured and I don't know why.

I have this problem too.
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andrew.burns Wed, 06/20/2007 - 04:02


The command is only relevant for Cisco IP Phones - if there is no phone connected the command won't do anything. I recall it sets some kind of flag in CDP to communicate with the phone so you need a Cisco IP phone and CDP enabled for it to have any effect.

As to why you have it on your WAN interface - maybe the port once had a phone attached?




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