No Outgoing Sound for Asterisk on Amazon AWS EC2

No Outgoing Sound with Asterisk on Amazon’s AWS EC2 Cloud

Recently, I have come across a few people with similar question:  Why they cannot hear any sound on the VoIP Phones when connecting to an Asterisk IP PBX that is located in Amazon’s AWS EC2 Cloud.  The issue is compounded by the fact that the IP Phones register with Asterisk and connects the call but no sound is heard.

This is usually caused by NAT setting in the sip.conf file under [general] context:

Since Amazon AWS EC2 uses NAT, those fields must be specified for Asterisk to work.  The fields that needs information are the localnet and externip.

Asterisk sip.conf NAT setting for Amazon AWS EC2 server







Now how do you find the localnet and externip on the Amazon EC2 server?  The externip would be the Elastic IP Address assigned which is readily available in the Amazon AWS Management Console.  That part is pretty simple and finding the localnet address is just as simple.

Type: ifconfig

Asterisk localnet information for Amazon AWS EC2 Cloud Server








You will see the inet address and the Mask information.  This information would be presented in the sip.conf as follows:

localnet = X.X.X.X/255.255.255.X
externip = Elastic IP Address

Once you have this setting in the sip.conf, reload the config in the CLI and try again.  This is a very simple fix but it is very easy to overlook.



About Express Interconnect: We are a Portland, Oregon based Small Business VoIP Phone Consultant specializing in implementing quality VoIP PBX system based on Asterisk IP PBX. We can be reached at 503-820-3513 or via email at: and can help with any questions you might have.

Due to Demand, we have finally branched out into Hosted VoIP Phone Service for Small Businesses.  Our Hosted VoIP Service provides full Asterisk IP PBX functionality in a simple Plug and Play system.

Also, please make sure to visit our on-line store at VoIP Phones Direct for all of your IP Phone needs. We carry Grandstream, Polycom, Snom, Aastra, and Yealink IP Phones with a 14 day money back guarantee and FREE UPS Ground Shipping.

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