sip.conf:

[general]
context=planlocal
srvlookup=no
disallow=all
allow=ulaw
allow=alaw
allow=ilbc
allow=gsm
language=fr
port=5060
bindaddr=0.0.0.0

[scruffy]
type=friend
username=scruffy
host=dynamic
secret=123456
context=planlocal
nat=no
canreinvite=no
quality=yes
dtfmode=rfc2833
allow=ulaw
allow=alaw
allow=gsm

[sam]
type=friend
username=sam
host=dynamic
secret=123456
context=planlocal
nat=no
canreinvite=no
quality=yes
dtfmode=rfc2833
allow=ulaw
allow=alaw
allow=gsm

-----

extensions.conf:

[planlocal]
exten => 1000,1,Dial(SIP/scruffy)
exten => 1001,1,Dial(SIP/sam)

-----

Errors Asterisk :

[Mar 23 18:00:05] NOTICE[22440]: chan_sip.c:15075 handle_request_register: Registration from '"1000"<sip:1000@scrufffy.eu>;transport=UDP' failed for '77.218.133.100' - No matching peer found
[Mar 23 18:00:09] NOTICE[22440]: chan_sip.c:15075 handle_request_register: Registration from '"1000"<sip:1000@scrufffy.eu>;transport=UDP' failed for '77.218.133.100' - No matching peer found

-----

Errors on my softphone :

17:51:16 Registering user 'scruffy@scrufffy.eu'
17:51:44 Timeout registration for 'scruffy@scrufffy.eu'
17:52:24 Timeout registration for 'scruffy@scrufffy.eu'
17:53:16 Timeout registration for 'scruffy@scrufffy.eu'