asterisk users - May 2005 - Q : registering sipXphone

Hello all,

I have problems trying to register sipXphone to asterisk. It always print
the message :

May 26 13:04:33 NOTICE[2781]: chan_sip.c:7691 handle_request: Registration
from
'sip:2503@172.25.50.52' failed for '172.25.49.219'

Anyone has an idea to help? Asterik seems to fail in register_verify() but i
don't know why...
My sip.conf is the following :

;
; SIP Configuration for Asterisk
;

[general]
port=5060
bindaddr=0.0.0.0
context=default
srvlookup=yes
dtmfmode=rfc2833
allow=all

[pingtel]
type=friend
username=2503
host=172.25.49.219
context=usercontext

Here are the SIP register exchange :

Session Initiation Protocol
    Request-Line: REGISTER sip:172.25.50.52 SIP/2.0
        Method: REGISTER
        Resent Packet: False
    Message Header
        From: sip:2503@172.25.50.52;tag=4f9a5597
        To: sip:2503@172.25.50.52
        Call-Id: 4c6b51cb68053520858d81947a06d592
        Cseq: 2146483648 REGISTER
        Contact:
<sip:2503@172.25.49.219;LINEID=3b16a663e2073901af0684024370ff1e>;EXPIRES=0
        Date: Thu, 26 May 2005 12:32:43 GMT
        Max-Forwards: 20
        User-Agent: sipX/2.5.2 (WinNT)
        Accept-Language: en
        Supported: sip-cc, sip-cc-01, timer, replaces
        Via: SIP/2.0/UDP
172.25.49.219;branch=z9hG4bK-d50a726004f399e09cce9dc984ab094e;rport
        Content-Length: 0

Session Initiation Protocol
    Status-Line: SIP/2.0 403 Forbidden
        Status-Code: 403
        Resent Packet: False
    Message Header
        Via: SIP/2.0/UDP
172.25.49.219;branch=z9hG4bK-d50a726004f399e09cce9dc984ab094e
        From: sip:2503@172.25.50.52;tag=4f9a5597
        To: sip:2503@172.25.50.52;tag=as4e32f2aa
        Call-ID: 4c6b51cb68053520858d81947a06d592
        CSeq: 2146483648 REGISTER
        User-Agent: Asterisk PBX
        Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER
        Contact: <sip:2503@172.25.50.52>
        Content-Length: 0

Thanks,
Christian.