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Webcast-Catalyst9k
New Member

qos - assign bandwidth for voip

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 10.100.1.0/24 network.

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

thanks

Carl

8 REPLIES
Hall of Fame Super Silver

Re: qos - assign bandwidth for voip

Hello Carl,

a possible example

access-list 111 permit udp 10.100.1.0 0.0.0.255 any range 16384 16384

access-list 121 permit tcp 10.100.1.0 0.0.0.255 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

Giuseppe

Super Bronze

Re: qos - assign bandwidth for voip

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.

Re: qos - assign bandwidth for voip

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?

HTH

Mohamed

New Member

Re: qos - assign bandwidth for voip

Hi there

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

Re: qos - assign bandwidth for voip

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 10.100.1.0 0.0.0.255 any range 16384 32767

access-list 121 permit tcp 10.100.1.0 0.0.0.255 any eq 1720

HTH

Mohamed

New Member

Re: qos - assign bandwidth for voip

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.

Hall of Fame Super Silver

Re: qos - assign bandwidth for voip

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

Giuseppe

New Member

Re: qos - assign bandwidth for voip

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.

Regards,

John Gill

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