asterisk users - Nov 2010 - Asterisk 1.6.2.13 IAX2 Realtime issue

Hi

I have configured IAX2 realtime in Asterisk 1.6.2.13.

when I cannect a client to realtime extension, always the state of extension 
is "UNKNOW" like:

  * Name       : marco
  Secret       : <Set>
  Context      : phones
  Parking lot  :
  Mailbox      : 2345 at default
  Dynamic      : Yes
  Callnum limit: 0
  Calltoken req: Auto
  Trunk        : No
  Encryption   : No
  Callerid     : "marco" <2345>
  Expire       : -1
  ACL          : No
  Addr->IP     : XXX.XXX.XXX.XXX Port 17143
  Defaddr->IP  : 0.0.0.0 Port 17143
  Username     : marco
  Codecs       : 0xc (ulaw|alaw)
  Codec Order  : (alaw|ulaw)
  Status       : UNKNOWN
  Qualify      : every 60000ms when OK, every 10000ms when UNREACHABLE 
(sample smoothing Off)

I tried with zoiper and DIAX softhone without success.

Any hint?

Thank's

- bakko