bbrindle,

Great news that you can use it with Asterisk. Then there is some hope. To answer your question, yes the extension is well set up in extensions.conf. In fact, I have tested the same extension with a Cisco 7940 and X-Lite and they both work.

My problem is really visible in the SIP communication where you can see that the sip-sofia stack is sending an Internal Server Error. I know that this can be because of a number of reasons though.

However, with your set up working I want to focus on the asterisk side. Do you mind posting your sip.conf for your N900 working extension?

Mine non-working is
[3450]
username=3450
type=friend
secret=xxxxxxxxx
qualify=500
nat=no
host=dynamic
dtmfmode=rfc2833
disallow=all
allow=ulaw
context=internal
canreinvite=no
callerid=Jonas HP <3450>

Also my general section is
[general]
canreinvite=no
; Include registers
#include "sip_register.conf"
dtmfmode=rfc2833
disallow=all
allow=ulaw
context=trunk ; Default context for incoming calls
allowoverlap=no
bindport=5060
bindaddr=0.0.0.0
srvlookup=yes
limitonpeers = yes
externip = xx.xxx.xxx.xxx
localnet=192.168.0.0/255.255.0.0
nat=yes

Thanks,

// Jonas