Callcentric and multiple DID Inbound routing [SOLVED]

Hi all,

I thought I'd post this message in case someone else is trying to accomplish the same thing with DID routing using Callcentric as a SIP provider.

My requirements were to use as little custom modification as possible and rely on Trixbox/FreePbx for everything else.

Background

You can get cheap DIDs with CallCentric however Callcentric stores the incoming DID identifier in the SIP header in the "TO:" field. So in Asterisk terms ${SIP_HEADER(TO)}.

This seems to cause problems for Trixbox as this is not where it seems to look for DID information.

In my case I have a few DIDs for my business and one for my home phone. I need to route any calls to my business DIDs into a time condition that will further route the call based on whether it's during business hour or not (this routing is handled by standard Trixbox and is not covered here). As for the home phone number, I want to route that to a ring group that will ring all of my home extensions (again, this ring group is setup the normal Trixbox way).

How to do it

In order to properly route calls based on the DID the caller dialed we need to add our own custom context to handle grabbing the correct DID number and routing on it.

The easiest way to do this is to place our contexts in the extensions_custom.conf file.

I'll write this so it will be easy for you to figure out how to handle your own situation.

First open up extensions_custom.conf in your favorite editor.

Add the following code and modify it to suite your particular situation (ie Your Callcentric number and DID numbers):

[custom-incoming]
exten => s,1,Set(Var_TO=${SIP_HEADER(TO)}) 
exten => s,n,GotoIf($["${Var_TO}" = <sip:1777XXXXXXX@callcentric.com>"]?timeconditions,1,1)
exten => s,n,GotoIf($["${Var_TO}" = <sip:15551234@ss.callcentric.com>"]?timeconditions,1,1)
exten => s,n,GotoIf($["${Var_TO}" = "<sip:15554321@ss.callcentric.com>"]?ext-group,200,1)
exten => h,n,Macro(hangupcall)

As you can see above, I've replaced my Callcentric id with Xs and used fictitious phone numbers. Obviously you'll want your own Callcentric account id and DID numbers in there.

The next step is to modify your default inbound route in Trixbox. You will need to set the destination of your inbound route to our custom context, using the Custom App: feature. So set the destination to be Custom App: with the following text:

custom-incoming,s,1

Once you apply the changes you should be all set!

Customizing

This custom context can easily be modified to route incoming calls to different contexts. I found the best way to figure out what Trixbox is calling a particular context is to temporarily set the incoming routes destination to the context I'm interested in, say a particular ring group or voice mail number. Then apply the changes and take a look at the extensions_additional.conf file and look for the "ext-did" context. We're interested in the last line of the context:

[ext-did]
include => ext-did-custom
exten => fax,1,Goto(ext-fax,in_fax,1)
exten => s,1,Set(__FROM_DID=${EXTEN})
exten => s,n,GotoIf($[ "${CALLERID(name)}" != "" ] ?cidok)
exten => s,n,Set(CALLERID(name)=${CALLERID(num)})
exten => s,n(cidok),Noop(CallerID is ${CALLERID(all)})
exten => s,n,Ringing()
exten => s,n,Goto(custom-incoming,s,1)

So in this case you can see by the last line there that our DID is routing to our custom-incoming context. But if you play around with your inbound routings you can see how it will refer to other contexts. For example, if I set the destination to be IVR: Main (my main Automated Receptionist) , the ext-did context revealed:

[ext-did]
include => ext-did-custom
exten => fax,1,Goto(ext-fax,in_fax,1)
exten => s,1,Set(__FROM_DID=${EXTEN})
exten => s,n,GotoIf($[ "${CALLERID(name)}" != "" ] ?cidok)
exten => s,n,Set(CALLERID(name)=${CALLERID(num)})
exten => s,n(cidok),Noop(CallerID is ${CALLERID(all)})
exten => s,n,Ringing()
exten => s,n,Goto(ivr-2,s,1)

Great! Now I know how to set my custom routing for IVR: Main. I just use "ivr-2,s,1" (your ivr number is probably different). Now setting the incoming route destination back to the Custom App: "custom-incoming,s,1". I can modify my custom-incoming context to route one of my other DID numbers by inserting the following line in my custom context:

exten => s,n,GotoIf($["${Var_TO}" = <sip:15551255@ss.callcentric.com>"]?ivr-2,s,1)

Just remember to restart or reload Asterisk after whenever you modify the extensions_custom.conf file or Asterisk won't see your changes.

Conclusion

So by just creating a simple custom context I can handle DID routing with Callcentric.
Hope this helps somebody out. I know I was frustrated with it for some time.