When I first was setting up a Skype Connect (Skype for SIP) trunk, I couldn't find any "I'm dumb, how do I do this" type articles and ended up reading several posts on doing it with asterisk and changing the "sip.conf" file. If you're not familiar with trixbox or asterisk, this can take time to get your head around it. The beauty of trixbox is you don't need to touch your config files and can easily set this up through the FreePBX GUI.
This is how to setup Skype Connect using trixbox.
After setting up a Skype Connect profile through the skype website, go to the trunks module within trixbox (logged in as maint).
Go to: PBX > PBX Settings > Trunks. Then click "Add SIP Trunk". (If I don't mention something this means to leave the default which is possibly blank.)
PLEASE NOTE: All incoming settings are blank!
-- General Settings --
Outbound Caller ID: 99051000xxxxxx – This is your Skype Connect registration ID
Maximum Channels: 1 – This is how many channels you purchased from Skype.
-- Outgoing Settings --
Trunk Name: SkypeConnect – This can be whatever you want
PEER Details:
username=99051000xxxxxx ; This is your Skype Connect registration ID
secret=xxxxxxxx ; This is your Skype Connect registration password
type=peer
qualify=yes
insecure=invite
host=sip.skype.com
fromdomain=sip.skype.com
disallow=all
allow=ulaw&gsm&alaw
context=from-trunk
fromuser=99051000xxxxxx ; This is your Skype Connect registration ID
-- Registration --
Registration String: 99051000xxxxxx:**password**@sip.skype.com/99051000xxxxxx
**password** is your Skype Connect registration password.
Click "Submit Changes"… Apply Changes.
This is all you need for setting up the registration to Skype Connect; you should now be able to log into Skype control panel and see "SIP user successfully registered at sip.skype.com".
Now you can go into your Extensions (PBX > PBX Settings > Extensions) module and make sure your SkypeIn number/s are attached to the correct Extension (you can have them go to an IVR/Call group/whatever but for the purposes of this will just go to an extension). Pick the extension (that you have already created or create a new one) then add the SkypeIn number as your "Outbound CID" and "Add Inbound DID"… Click "Submit"… Apply Changes.
Outbound Calling – Go to: PBX > PBX Settings > Outbound Routes.
From here you want to map your outbound calls to go across your Skype Connect trunk that we setup earlier. Either create a new route or edit the default one… Under "Dial Patterns" (we'll use dial 9 for an outside line/use this trunk) add "9|." minus the quotes. Set the "Trunk Sequence" to "SIP/SkypeConnect". Click "Submit Changes"… Apply Changes.
That's It! – You should now be able to make and receive calls to and from the outside world with your trixbox and extension. If you get stuck, i've missed something or have question feel free to contact me.