Monday, December 26, 2011

VoIP "Can't Hear Me, Can Hear Them" Issue


You have (deployed) a SIP VoIP telephone set (can also be a software SIP phone) at home. Your phone rings and you can even dial out but the recipient of a call cannot hear you, though you can hear the recipient's voice.


(1) This means that the SIP protocol is going though but the RTP protocol is not going through. This happens in a typical home WiFi "router" scenario connected to cable or DSL service.

(2) Has your phone been in your corporate office or a branch office? Sometimes, these phone are set behind an "EDGE BOX" that provides different protocols and have different codes in the firmware. 

Possible Fixes:

If your situation applies to (2) above then you need to call your IP service provider, explain to them that you have moved your phone from your office to home and requires a "Push of new config to your phone."

Below applies to everyone. In most cases the blocked UDP by your wireless router is the key! 99% of the case this is it.
Most people use a wireless router at home. However this will cause an issue as most of them prohibit UDP protocols to go through via their built-in firewall. Thus it is time for you to learn to open up firewall settings on your router.

If you cannot make a call at all or if you cannot receive any calls at all: Check UDP 5060-5063 ports.

If the sound is an issue then try opening UDP Port 16384 - 16482, or 10000 - 20000. This depends on the phone implementation.

Note: If you are an Astound customer, try connecting the phone directly to the DMZ port provided by Astound.

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