Switching to VoIP

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Chapter 15: What Can Go Wrong?

system. But if the trunks used for the new system have the same phone numbers as

those used with the old system, you could be in a mess. This is because they can’t be

connected to both systems (old and new) at the same time. If they could, switching

PSTN connectivity from one trunk group to another wouldn’t be such a critical task.

Here’s how you can avoid a botched trunk move turning into phone downtime:

1. Don’t switch over all of your inbound phone numbers to a new trunk circuit.

Bring over only the “main” numbers—the numbers the outside world knows.

That way, if the switchover doesn’t happen, you’ll still have usable (secondary)

outbound trunks on the old system. You’ll have to worry about inbound traffic

only to those “main” numbers.

2. In the event of a failed switchover, first determine whether you still have dial-

tone on your old trunks. If you do, you can continue to use them with your old

system until the switchover can be rescheduled.

3. If the old trunks don’t have dial-tone any longer and the new trunks aren’t work-

ing, have the phone company forward all calls destined for those “main” inbound

numbers at the CO to the secondary trunks that you haven’t switched over.

These trunks are, hopefully, still connected to your old system. (See ...