asterisk users - Jan 2010 - forward call back up same trunk to external cell phone problem

Hi

If I have an incoming call coming down a SIP trunk to a particular
internal SIP extension- I can answer the extension fine, all works
well

However, if I change extension.conf from dialling the internal
extension to forward the call to an external cell phone (up the same
trunk as the incoming leg of the call) I cannot get any audio and get
the following error message on the console:
[Jan 30 08:38:42] WARNING[27575]: rtp.c:1145 ast_rtp_read: RTP Read too short

i.e. change from
[voipfone_incoming]
exten => s,1,Dial(SIP/203,20,t)

to
[voipfone_incoming]
exten => s,1,Dial(SIP/07123123456 at voipfone,20,t)

What's wrong?!

John

Hi- can anyone help with this. I'm really stuck as apparently it
should work. Is it a problem with the ITSP, with using the same trunk
for both legs of the call etc?

John

On 30 January 2010 08:57, John Taylor <john at vetsurgeon.org.uk>
wrote:
> Hi
>
> If I have an incoming call coming down a SIP trunk to a particular
> internal SIP extension- I can answer the extension fine, all works
> well
>
> However, if I change extension.conf from dialling the internal
> extension to forward the call to an external cell phone (up the same
> trunk as the incoming leg of the call) I cannot get any audio and get
> the following error message on the console:
> [Jan 30 08:38:42] WARNING[27575]: rtp.c:1145 ast_rtp_read: RTP Read too
short
>
> i.e. change from
> [voipfone_incoming]
> exten => s,1,Dial(SIP/203,20,t)
>
> to
> [voipfone_incoming]
> exten => s,1,Dial(SIP/07123123456 at voipfone,20,t)
>
> What's wrong?!
>
> John
>