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802.1p on 3750 ingress COS tag vs Egress COS tag


Hopefully someone will have some insight in to this.

I have a 3750 configured for switchports to trust the cos value recieved from the device it is connected to. When I run Ethereal, I am seeing the COS tags with a correct value that was assigned. What I am NOT seeing is egress traffic on the port retain or assign any value. What am I missing?? The switchport config is below.

interface GigabitEthernet1/0/3

switchport voice vlan dot1p

duplex full

mls qos trust cos

spanning-tree portfast

ip igmp max-groups 130


Re: 802.1p on 3750 ingress COS tag vs Egress COS tag


where does the return traffic come from? Just make sure to set all trunk ports to trusted as well. Also you might have an issue with DSCP-to-CoS mapping or vice versa.

Can you post your complete QoS config please!?

Hope this helps! Please rate all posts.

Regards, Martin

New Member

Re: 802.1p on 3750 ingress COS tag vs Egress COS tag

Thank you for the reply.

Currently I believe the source and destinations are within the same switch so no trunkports should be doing the COS rewrites. I have thought about the default DSCP-COS maps possibly rewriting the values but as you see in the QOS config (which is very basic) that should not be happening.

Here are the global QOS config.

mls qos

no mls qos rewrite ip dscp

Tonight I will be verifying that the VLAN ID assignment form the server matches the voice VLAN ID. Also I am going to ask my co-worker (server guy) to let the vlan assignments and COS tags come from the switch as opposed to the server.

I look forward to more input!



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