Re: Layer 2 QOS COS marking on Inbound

Thanks.. is the cos to dscp conversion done automatically. Does this apply
to a Router as well?

On Mon, Jul 18, 2011 at 12:37 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar>wrote:

> COS is not carried from input to output, but instead, converted to internal
> DSCP using cos-to-dscp if cos is trusted on input or
> override is used.
>
> On output, its value is mapped using dscp-to-cos and set on the egress
> frame if the frame supports it.
> DSCP is also reset unless pass through is used, or modified by some exit
> policy.
>
> But make yourself a favour and test it. That's the best way to learn it!
>
> -Carlos
>
> Irfan Sid @ 18/07/2011 01:58 -0300 dixit:
>
>> Hi Group.
>>
>> On the Cisco switches (2960) can I apply layer 2 COS marking inbound on a
>> Dot1q trunk, or can it be applied outbound only?
>>
>> I understand when a Frame comes inbound on a Trunk, the Vlan tag is
>> removed,
>> so dot1p cos cannot be applied.
>>
>> On the outbound, the VLAN tag is added on a trunk and 802.1p COS value can
>> be attached to the frame.
>>
>> Is this understand correct.
>>
>> However, I have seen mls qos cos <value> override, applied on voice vlans
>> on phone ports so not sure if the cos is written to the frame and
>> classified
>> before the vlan tag is removed on the inbound.
>>
>> Please can someone correct my understanding?
>>
>>
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>>
>>
>>
>>
>>
> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina

Blogs and organic groups at http://www.ccie.net
Received on Mon Jul 18 2011 - 13:28:02 ART