qos - assign bandwidth for voip

Unanswered Question
Sep 7th, 2009

Hi all

on my router, I have a 2 meg wan link, I want to assign 1 megabit for the voip payload, and remaining 10% for the signalling.

the codec is g711, and I want to match on source address of network.

can anyone tell me how to do this with the bandwidth using class / policy map etc.



I have this problem too.
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Giuseppe Larosa Mon, 09/07/2009 - 07:23

Hello Carl,

a possible example

access-list 111 permit udp any range 16384 16384

access-list 121 permit tcp any

class-map voip_bearer

match access-group 111

class-map voip_sign

match access-group 121

policy-map llq-out

class voip_bearer

priority 1000

class voip_sign

bandwidth 200

int ser0/0

service-policy out llq-out

Hope to help


Joseph W. Doherty Tue, 09/08/2009 - 04:00

If you want to truly insure class voip_sign obtains its defined bandwidth, on many Cisco platforms prior to HQF would suggest FQ, within class-default, be changed to FIFO.

Mohamed Sobair Mon, 09/07/2009 - 08:19

Hi Carl,

Could you please be more precise? do you want to police the voip traffic out of the two meg? Or you just want to ensure VOIP traffic a maximum of 1 Meg whenever congestion occurs?



carl_townshend Tue, 09/08/2009 - 00:51

Hi there

I want to make sure the voip has at least 1 meg if there is congestion!

Mohamed Sobair Tue, 09/08/2009 - 01:54

Hi Carl,

Ok, the config provided by Guiseppe should be sufficient but i would modify the previous access-list to the following:

access-list 111 permit udp any range 16384 32767

access-list 121 permit tcp any eq 1720



ralphcarter Tue, 09/08/2009 - 04:21

Carl, using the "priority 1000" command will guarantee voip uses 1 meg at times of congestion and it will be the first out of the queue. If there is no congestion then voip will be able to use more than 1 meg but anything over this 1 meg will not be guaranteed and will be dropped if congestion occurs.

When you configure voip, you normally set it using the llq with the priority command but make sure you set it to a sufficient limit.

Giuseppe Larosa Tue, 09/08/2009 - 06:44

Hello Mohamed,

thanks for correcting the first ACL I did a mistake in writing it.

I may be wrong but from other posts from Carl I have the impression that his phones are not Cisco IP phones and they don't talk with a Cisco Call Manager with SCCP.

For this reason I preferred to leave undefined the TCP port for signalling.

What John says is correct we should have more details to provide a configuration that will work.

Hope to help


johgill Tue, 09/08/2009 - 04:31

This depends on the device - the suggestions in this thread will work for many routers, but not likely for most switches.

We would need the platform, linecards for the LAN and the WAN link (if applicable), and version information.


John Gill


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