[asterisk-users] Redirect call based on CLI???

[Brian]

This is a real 'newbie' type question, but I can't get my brain to work
today.

Is it possible to re-direct an incoming SIP call based on it's CLI?

Ideally I would like to check incoming calls against a short whitelist
(of say 20 numbers) and redirect to a different extension if there is a
match.

I would also like to redirect calls that fail to present any CLI (aka
WITHHELD/UNAVAILABE) to a different extension

At I guess I would suspect I could implement this - can someone give me
a starting point?

Many thanks
Brian