I am new to Asterisk. Trying get a SIP only system up for the first time. I am running version 1.4.25 loaded on Fedora core 10. I have modified sip.conf and extensions.conf per recomendations. I have tried X-Lite and Cisco 7960, but they will not register. With Wireshark (on PC) I can see the Register msg going out. With tcpdump I can see the Register msg coming in to the Linux server. But when I go to the Asterisk console there are no sip msgs at all. Please help. Thank you.
You would get answer faster if you post your sip.conf and output from console after entering “sip set debug” 
I have entered “sip set debug” but there is no output at the console. Here are the sip.conf and extensions.conf files. Please let me know if there is any other info I can provide. Thank you.
sip.conf:
[general]
context=default
allowoverlap=no
bindport=5060
bindaddr=0.0.0.0
Here is my sip.conf
[1001]
type=friend
username=1001
context=phones
host=dynamic
secret=guessthis
[1002]
type=friend
username=1002
context=phones
host=dynamic
extensions.conf:
[internal]
exten => 1001,1,Dial(SIP/1001)
exten => 1002,1,Dial(SIP/1002)
[phones]
include => internal