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Limit Data Bandwidth on VoIP

We are an US based international call centre.We are using cisco AS5300 as our VoIP gateway. I would like to know if i can use the same AS5300 for internet as well. If yes how can i limit the bandwidth out of the total bandwidth i have for data i.e. internet.Please let me know at the earliest.


Re: Limit Data Bandwidth on VoIP


You can CBWFQ on your interface-facing interface to greater a certain amount of bandwidth to your voice traffic. The rest can then be used for your internet traffic.

The one thing that you cannot effectively do is to control your incoming traffic. Most ISPs will not distinguish between voice and data traffic and so, in the inbound diretion, there will be indiscriminate drops at the ISP's interface to you (in the event of congestion).

The following link has more details on CBWFQ:

Pls provide more info what you require if you need more detailed answers.

Hope that helps - pls rate the post if it does.



Re: Limit Data Bandwidth on VoIP


as an additional info to the previous post: I would recommend to use LLQ for voip traffic.

Not only a certain amount of bandwidth but also low delay are important for voip traffic.

So outbound you could use a policy like this:

ip cef

class-map match-any VoIP

match ip dscp ef cs5

match protocol rtp audio

class-map match-any VoIPsignal

match ip dscp cs3

policy-map VoIPprio

class VoIP

priority percent 10

class VoIPsignal

bandwidth remaining percent 5

class class-default



interface Serial0

ip address ...

service-policy output VoIPprio

You would have to adjust the bandwith ratios for your needs and the interface naming to your environment.

The policy will give 10% of the link to voip traffic with lowest possible delay, 5% of the rest for voip signaling, and the rest for the other data present.

Again as already mentioned your ISP controls the interface towards you and you might need his helps to solve potential voip qos issues arising from dropped packets on his side.

Hope this helps! PLease rate all posts.

Regards, Martin

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