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New Member

QOS -- Unused bandwidth of priority class

Hello Expert

Our customer has a router which will be installed a 2M WAN link to connect another site. Because of the voice service will be implemented in local site, we are planning to implement QOS on the Wan link as below

50% bandwidth of WAN link for Voice (we say that it is priority class, priority command will be issued to the class)

30% bandwidth of WAN link for Data (we say that it is bandwidth class, bandwidth command will be issued to the class)

Other % of bandwidth put into default class

My question is, when the voice traffic only loaded 50% of prority class, Other classes whether can use the rest of % bandwidth of priority class?

Many Thanks

New Member

Re: QOS -- Unused bandwidth of priority class

The remaining bw not used by the priority class will be distributed among other classes as needed.

Cisco's definition of bandwith vs priority command: " Although the bandwidth guarantees provided by the bandwidth and priority commands have been described with words like "reserved" and "bandwidth to be set aside", neither command implements a true reservation. In other words, if a traffic class is not using its configured bandwidth, any unused bandwith is shared among other classes".



Re: QOS -- Unused bandwidth of priority class


first 50 % + 30 % = 80 % is > 75 %, the ios will not let you go with this config remember you have a marge of 75 % of the configured bandwidth to play with the other 25% is reserved for system use unless you touch the max-reserved-bandwidth and cisco does recommand to change that 25 % of control protocol and system use or you use the percent command with priority or bandwidth in this case 50 % will be 50 % of 75 %....

the other question i m agree with what is posted .


do rate if it does help

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