c2900XL and QoS (CoS)

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Mar 24th, 2008
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HI,

I have a cisco 2924xl with the latest IOS for that model.


I have connected a IP Phone with CoS f 5 enabled on the phone.


Does this switch model support trusting of CoS from the incoming traffic?


If so, how do i set it up?

thx

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glen.grant Mon, 03/24/2008 - 05:27
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That switch is ancient and EOL , I doubt a switch from that era supported any of those type parameters.

Jon Marshall Mon, 03/24/2008 - 06:17
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Hi


Don't know which IOS version you are running but this commmand reference suggests you may be able to. Command would be


switchport priority extend trust


See attached link for full details


http://www.cisco.com/en/US/docs/switches/lan/catalyst2900xl_3500xl/release12.0_5_wc_1_/cli/clicmds.html#wp1058076


HTH


Jon

rsabapathee Mon, 03/24/2008 - 21:42
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The commnand 'switchport priority extend trust' is also valid on a 802.1q trunk port.


What is the logic behind this?? What is the point of enabling this command on a trunk port?

Jon Marshall Tue, 03/25/2008 - 00:35
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Hi


Actually it's the other way around. If you are trusting CoS markings then they will only be present on a 802.1q trunk port because the 802.1p CoS markings are contained within the 802.1q vlan tag. That's why when you connect a phone + pc to a switchport that switchport is configured as a trunk.


Jon

rsabapathee Wed, 03/26/2008 - 21:17
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OK. So its the trunk port which takes notice of the CoS marking.


1. So I only need to enable this command on trunk ports??


2. I connect an IP Phone on fa0/1. PC is connect to Fa2 of IP Phone. Both are on native vlan. The phone has in-built capability to do CoS marking.

Do I need to enable CoS on fa0/1 or on the trunk port which carries the traffic to the next switch?


3. Cisco switch A on port fa0/1 is connected to Cisco switch B on port fa0/24.

Devices connected to switch A do CoS marking.

On which ports do I need to issue the command 'switchport priority trust cos' for the traffic from the specified devices to be given priority.


thx for the clarification.

rsabapathee Thu, 03/27/2008 - 10:57
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4. If all traffic are on native vlan. A non-Cisco IP Phone connected to the switch (fa0/1) does CoS marking.

Is the traffic from the device given priority at the egress of the trunk port (to another switch) or at the egress of the fa0/port?


I hope the experts can clarify my ambuigity.


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