[Asterisk-Users] Home users

Rich Adamson
Sun, 21 Mar 2004 19:25:13 -0000

> >From the 7960 at my home I get connected.  I can then call any other
> phone in the office and call outside calls.  The problem is as soon as
> someone picks up their office phone there is dead silence.  The office
> phone can call my home phone and it rings and again when I pick up the
> home phone there is nothing.  I do have port forwarding turned on my
> office firewall.
>
> Can someone help me here?  I am almost out of hair on my head.

The problem is a very common one. The 7960 uses the sip protocol to
communicate with asterisk using udp 5060. The phone will attempt to
negotiate "another udp port" to handle the voice (rtp) protocol, and
on the Cisco, that port can range between 16384 and 32766 (defined
in SIPDefault.cnf file).

The 7960 might choose udp 33333 while asterisk might choose udp 44444.
Your firewall does not know these ports were selected and therefore
blocks the rtp traffic.

Check out the various nat parameters for asterisk (and the phone) as
a mechanism around the problem. In some cases, having a packet sniffer
such as ethereal will help you understand what is really going.