End-to-End Switch QoS

From: Yasser Aly (blackyeyes00@hotmail.com)
Date: Mon May 10 2004 - 18:38:55 GMT-3


Hello,

   Scenario is as follows: VLAN 4 is configured on many ports on the switch.
One of the ports is connected to a server providing multicast feeds with a
CoS value of 4.

Required:

1) Maintain multicast feed CoS value received at this port as it enters the
switch block.

2) Other ports that belongs to VLAN 4 should be marked with a CoS value of 1
to avoid getting any better treatment.

Solution Provided:
---------------
mls qos
!
int f0/4 ( Where the server is connected )
mls qos trust cos
!
int f0/8 ( Other port belongs to VLAN 4 )
mls qos cos 1
mls qos cos override
-----------------

My questions:

1) Will there be a difference if I used  switchport priority extend cos 1 
instead of using  mls qos cos 1  + mls qos cos override  on other ports
that belongs to this VLAN other than the server port ?

2) If the scenario has 2 switches and this VLAN has ports on both switches,
will there be any configuration needed to the trunk ports to maintain the
CoS value or I just need to care about the entry point and that's it ? What
are the guarantees that the CoS values will be maintained between both
switches ?

3) Finally, on the port having the server. Is it possible to assign two
differnt CoS values on the same port ( One for the mcast feed, and other for
the rest of traffic ) ?

Your feedback is highly appreciated.

Yasser



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