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Let's say a businessses purchases a sufficently fast internet connection (such as 60Mbps cable connection) and VOIP quality is pretty good for the most part. The only thing I would be worried about is a user initiating a file download and saturating the line. Would it be possible to restrict bandwidth on a per-port (logical port) basis. For example 5 Mbps is reserved for SIP traffic and the maximum a file could download at is 55Mbps. The setup would look like:

 FreePBX --------> Cisco Router -----> Internet (SIP provider is here)
 Users ----------> /\
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What is a "logical port"? – David Schwartz Aug 13 '13 at 0:47
A port number (port 8080) as opposed to a physical port (Gi0/0). I want to limit bandwidth so that the port for SIP connections is allocated 5Mbps and all others can saturate the (line - 5Mbps) – network-tech Aug 13 '13 at 13:05


Make an access-list and class to match the traffic you're interested in

ip access-list extended VOIP
 permit udp any any range 16345 65535

class-map VOIP
 match access-group name VOIP

Create a queuing structure for your important traffic and give it priority in times of congestion:

policy-map QUEUING
 class VOIP
  priority 5 mbps
 class class-default

Finally, create a shaper to limit your upstream to match what you pay for (this will force the queuing to happen on your equipment instead of upstream in the provider where they'll drop whatever they want (including your voice);

policy-map SHAPER
 class class-default
  shape average 60 mbps
  service-policy QUEUING 

Finally apply the policy map outbound on your router interface that faces the internet

int gig 0/0
 service-policy output SHAPER
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This Cisco documentation leads me to believe that yes it is possible.

That applies to ios12.2, I didn't see any mention of it being device specific.

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