Welcome to the forum. Do you plan to use the Comcast number as a forwarding number for GV? If so the Comcast number must be able to ring.
If you use the Comcast number for outgoing calls it will show the Comcast number as caller ID.
Does your subscription plan on Comcast offer
Call forwarding?One possible solution.
you could get a free CallCentric DID, and fwd your Comcast calls to CallCentric Voicemail
but your phone will probably ring once, every time a call was forwarded
What he said. Actually it won't ring at all if you place this in the inbound callroute for the line port. For the example we are assuming SP2 is a sip provider and we are assuming you decided to use Callcentric. 177xxxxxxxx or xxx represents an extension you created on Callcentric that goes directly to voicemail. If you use a SP not actually registered to Callcentric use the first example. If you use a SP registered to Callcentric(same account you are forwarding to) use the second example.
{sp2(
177xxxxxxxx@in.callcentric.com)}
or
{sp2(
xxx@callcentric.com)}