Re: Layer 2 QOS COS marking on Inbound

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