Asterisk and Home Office User

Hallo Asterisk Support.

First, sorry for my bad english, im from austria.


We got an Asterisk installation (Gemeinschaft) which works fine.
But now we have an employee who works at home and he needs his fone with his direct dialing (11)
Now we set all Ports open from His Public IP to the Lokal IP of the asterisk sever.
Our Asterisk Server got an Public IP too (NAT on Firewall)
And the employee got a speedtouch business router which is set PPPoE Passthrough aswell and behind that router there is a Fritzbox 7270.
On this “Fritzbox” he types in the IP Adress of our Asterisk Server, his intern username (11) and the Passwort (Sip passwort).
I can see he is getting online with his fone and we can call him with his direct dialing (11).
But when he pick ups the phone there is no speedtransfer. we hear nothing.
So ive double checekd the Firewall Settings an he double checkt his Fritzbox Settings and we dont know where to look now.

Have u any idea or can u help us ?

Maybe one asterisk log will help, but i dunno if this has something to do with the problem:

[Oct 5 15:21:52] WARNING[2648] chan_sip.c: Hanging up call 0092CBBE93681F7B@x.x.x.x - no reply to our critical packet.
[Oct 5 15:22:39] WARNING[2648] chan_sip.c: Maximum retries exceeded on transmission C8D313F94F36D532@x.x.x.x for seqno 390 (Critical Response)

The x.x.x.x. stands for his Public IP of the speedtouch router!

with regards