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QoS Priority Percent

Hi All, 

We are trying to create 3 QoS queues for a WAN circuit between a managed CE and the PE in our network. 


Currently we have:

policy-map PM_WAN_OUT
class CM_VOICE
priority percent 30
set ip dscp ef
bandwidth percent 30
set ip dscp af31
class class-default
bandwidth percent 40
set ip dscp 0
random-detect dscp-based


With the idea that VOIP and signalling has a LLQ of 30%, critical data has 30% and everything else has 40%.

We've done a little testing and can see that the LLQ gets 30% of the bandwidth, however, if there is no traffic in the LLQ, will the other queues be able to use that bandwidth? For example, if there were no voice calls, or critical data (queues 1 and 2) then the default class could have 100% of the bandwidth? 

Also, is it best practice to map DSCP to EXP for transmission over our MPLS network, or use mls qos trust dscp instead?

Thanks for the help

  • Voice over IP
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Super Bronze

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In answer to your first question, normally, "unused" class bandwidth is available to other classes.  So, yes, also normally, the default class might use 100% of the bandwidth (if none is being used by other classes).

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