04-02-2007 10:49 AM - edited 03-05-2019 03:15 PM
Hi all, when tagging the traffic using cos at the layer 2 level, how do we tell the switch etc what kind of traffic we want to give a priority too, ie if we want to tell it to look for voice then apply the relevant policy, how would we do this ?
cheers
04-02-2007 11:48 AM
Hello,
Under the switchport you issue the command
"mls qos trust Cos". The switch will then start looking at the COS tag and according to the tag it will prioritize the traffic.
Hope this helps,
Appreciate your rating,
Regards,
04-02-2007 02:09 PM
thanks for that, so how do we tell cos that the paticular traffic is voice ?
04-02-2007 03:07 PM
Normaly, VoIP phones, mark the CoS value in their L2 frame.
For example you might have the topology
Phone --- L2switch --- Router1
If the phone is setting the CoS value you just need to trusted on the L2 Switch.
Then on the Inbound Interface between L2 switch and the Router you need to convert the CoS value to a DSCP value.
This dscp value later can be matched on oubound policy on LLQ.
Example;
Service-policy inbound (between switch and Router)
Class CONE
match cos 5
policy-map PONE
class CONE
set dscp 40
Later on the Router outbound serial interface
service-policy outbound PTWO
Class CTWO
match dscp 40
policy-map PTWO
class CTWO
priority 64
...
Hope this helps!
04-03-2007 12:19 AM
thanks for that, so are we saying here that the phone or whatever device you plug in has its own set cos value, and all you do is tell the switch to trust it ? can you set the qos on the switch ?
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