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Your answer solves the problem, thank you very much :D
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Your answer solves the problem, thank you very much :D

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I have a problem with the external extensions of my PBX Asterisk.<br />
<br />
Inside my office’s intranet everything works perfectly with the SIP Numbers and extensions, tested on the Grandstream and YeaLink telephones. It also works perfectly on Softphones such as Zoiper and X-Lite.<br />
<br />
The problem is when you try to connect to an external or remote extension, the necessary ports are already open (5060 and UDP 10000-20000), and the Softphone programs are registered correctly on the PBX. While dialing to another extension or a conventional number the link is established and the phone rangs, but when the call is answered neither of us is able to listen anything.<br />
<br />
Eventually the call ends, 5 to 20 seconds later after.<br />
<br />
I’ve been told that I might have the RTP protocol blocked in my D-link router DIR-857.<br />
<br />
Does anyone know what could be happening?
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I have a problem with the external extensions of my PBX Asterisk.

Inside my office’s intranet everything works perfectly with the SIP Numbers and extensions, tested on the Grandstream and YeaLink telephones. It also works perfectly on Softphones such as Zoiper and X-Lite.

The problem is when you try to connect to an external or remote extension, the necessary ports are already open (5060 and UDP 10000-20000), and the Softphone programs are registered correctly on the PBX. While dialing to another extension or a conventional number the link is established and the phone rangs, but when the call is answered neither of us is able to listen anything.

Eventually the call ends, 5 to 20 seconds later after.

I’ve been told that I might have the RTP protocol blocked in my D-link router DIR-857.

Does anyone know what could be happening?

Audio problems with remote extensions on asterisk

Voice over IP (VoIP) is a methodology and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms commonly associated with VoIP are IP telephony, Internet telephony, broadband telephony, and broadband phone service. The term specifically refers to the provisioning of communications services (voice, fax, SMS, voice-messaging) over the public Internet, rather than via the public switched telephone network (PSTN).  Examples of the VoIP protocols are H.323, Media Gateway Control Protocol (MGCP), Session Initiation Protocol (SIP), H.248 (also known as Media Gateway Control (Megaco)), Real-time Transport Protocol (RTP), Real-time Transport Control Protocol (RTCP), Secure Real-time Transport Protocol (SRTP), Session Description Protocol (SDP), and Inter-Asterisk eXchange (IAX).

Voice Over IP

IP telephony (Internet Protocol telephony) is a general term for the technologies that use the Internet Protocol's packet-switched connections to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated circuit-switched connections of the public switched telephone network (PSTN). Using the Internet, calls travel as packets of data on shared lines, avoiding the tolls of the PSTN. The challenge in IP telephony is to deliver the voice, fax, or video packets in a dependable flow to the user.

IP Telephony

A router is a networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet. The most familiar type of routers are home and small office cable or DSL routers that simply pass data, such as web pages, email, IM, and videos between computers and the Internet. More sophisticated routers, such as enterprise routers, connect large business or ISP networks up to the powerful core routers that forward data at high speed along the optical fiber lines of the Internet backbone. Though routers are typically dedicated hardware devices, use of software-based routers has grown increasingly common.