Number forwarding and call redirects

Has anyone implemented Number forwarding or call redirects with asterisk on a large scale?

What I need to know is, Does asterisk have to answer the call and then forward the call to the new number …therefore incuring new call charges?

Is it possible to redirect/forward the call to the new number without answering inorder not to have to continue to process the call or incure call charges?

is this in anyway possible?

For this type of application you are probably better off using something like OpenSER. Some examples here:

Having said this, it is possible for Asterisk to redirect a call to another location without answering the call (assuming it is a SIP/IAX originated call). This may be done by simply doing this:

exten => s,1,Ringing
exten => s,2,Dial(SIP/…)

As long as you are allowing for reinvites this call will be connected and then drop out of the Asterisk SIP dialog.

What if it is PSTN/PRI originated call?

Then you would need SS7 internetworking with your network provider if you want to redirect calls within the PSTN. Otherwise, your Asterisk server must answer the call and actively stay in the stream to maintain the PSTN/PRI channel with where ever you are redirecting the call to, otherwise known as tromboning.

cool…thanks buddy