[cisco-voip] Conversion from Centrex to VoIP

[Jason Roysdon]

I have another solution that makes switching over rather nice as well:

When you BAT in the phones, set the CFwdAll to dialing their Centrex
number, using whatever method works (probably using your outside dialing
digit + Centrex extension).

Then, any Cisco phone calling that phone, even if the Cisco phone is
sitting on the desk and otherwise working, will automatically forward to
the Centrex number.

You can then cut phones over on a per-phone basis very easily from the
Cisco side.  You just remove the CFwdAll and now the Cisco phone works
as expected from the Cisco side.  This can be done at the desk itself as
you deploy phones, or en mass with BAT.

Of course, you still have to do your Centrex porting/moving.  I've
another trick for that w/o having a "flag day" where everything has to
move at once:

If you have new DIDs or can get temp DIDs, you can forward from the
Centrex phones to the temp DIDs pointing to the Cisco phones and then
unplug Centrex phones (of course, you need to un-CFwdAll the Cisco
phone, or you'll have a loop back to the Centrex phone which will loop,
etc.).  When you're all cutover, you'll have the typical porting of
Centrex numbers and can then discontinue using the temp DIDs.  So long
as the telco doesn't mess this up (count on it that they will), your
users won't even know.

While this seems complex, I've used it at a number of customers who
couldn't just move entire DID blocks as they were given to different
departments or had other requirements of slowly moving things over.  It
works for non-Centrex moves off of PBXs as well (using a voice gateway
in between the old PBX and the PSTN).

Jason Roysdon
http://Roysdon.net/

Lisa Notarianni wrote:
> I asked this question before but did not get a response from anyone.  I
> am going to reword it...
> 
> We are in the process of switching from Centrex to VoIP.  As we move
> along and convert each department, we find timing difficult because as
> soon as the phones are entered in Call Manager, those already on VoIP
> calling the lines on that phone get an error since the phone is not yet
> plugged in.
> 
> In addition to having convert the lines from Centrex to our DID block (I
> can work around that), we find it difficult to come up with a solution
> with being able to work ahead of schedule by adding the phones into Call
> Manager without having calling issues from VoIP phones. 
> 
> Anyone know of a creative way to add these phones to Call Manager but
> isolate them from other VoIP phones until we are ready to deploy them to
> desks? 
> 
> Thanks,
> 
> Lisa
> 
> 
> 
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