No subject

is the case, try changing it to 'externip=54.241.129.14'.  You should
also set localnet as follows:

  ; RFC 1918 addresses
  localnet=192.168.0.0/255.255.0.0
  localnet=10.0.0.0/255.0.0.0
  localnet=172.16.0.0/12

If that doesn't work you can also try setting 'nat=force_rport'
instead of 'nat=yes'.

> [7001] 
> type=friend 
> host=dynamic 
> secret=123 
> context=internal 
> 
> [7002] 
> type=friend 
> host=dynamic 
> secret=456 
> context=internal 
> 
> A snoop capture for my call is uploaded in the following link. I
> wonder if there is any missing configuration or plugin need to be
> set here! 
> http://www.fileconvoy.com/dfl.php?id=gc0957418962ed157999374318118ae80b9d015992 

At this point, you should be able to establish a call between the two
X-Lite phones that won't get disconnected due to failing to complete
the three-way handshake.  There may still not be voice because the
firewall(s) between Asterisk and the X-Lite phones may block the RTP
traffic.  The phones appear to be on the same network, so you can try
setting 'canreinvite=yes' to workaround this problem until the
firewall(s) are configured to allow RTP traffic on the UDP port range
specified in 'rtp.conf' (the default range is 10000-20000).

Good luck and please report your progress back to the list.

Regards,

Matthew Roth
InterMedia Marketing Solutions
Software Engineer and Systems Developer