Newbie Question: Don't Understand Fully How Delivers Call Paths

I have purchased service from I ask for 8 call paths. I wanted 7 call paths on one trunk (for voice) and 1 call path on another trunk (for fax). The sales rep said that for 1 call path = one trunk. Ok so far.

When I get setup I get information to enter into FreePBX. gave me information for a primary and a secondary trunk. All call paths on these trunks.

What I don’t understand is this: If I use one of the 8 DIDs I have for a fax machine and it is busy sending/receiving a fax what keeps a new call to it from rolling into the voice lines if someone tries to send me a fax during that call? Does that make sense?

I have had trunks with Aretta and they gave me a trunk for the fax and a trunk for the voice. There is no way for the two to be aware of each other so if a fax rings in and it is busy the calling fax machine gets a busy signal.

Thanks. Keep in mind I am a newbie so please don’t assume I know what you are talking about - you can talk to me like I am a four year old and I won’t take offense at all.

your understanding is correct.

with CW disabled and no voicemail configured for the given extension, it will simply send back BUSY.

Thank you Philippe for the explanation. That helps me a lot. I still don’t fully understand I guess the part of how multiple calls into a single DID are going to work for the fax machine. Really I’m not sure I have too.

For instance. I have 8 DIDs from But I am only giving out one for voice and one for fax (after I get this figured out). On the voice I have tested and many calls will ring into that single DID I am giving out as the main number. The fact is I really only needed 2 DIDs but I got 8.

My concern is that the same thing will happen on the fax DID when I start publishing it. If the line is in use I am concerned that it will “roll” or “hunt” to one of the other call paths and be delivered into the voice side of the system. If I am understanding you … this is not possible.

So here is what I understand you are saying. If I give out one of my DIDs as a fax number and my PBX is routing that DID to a specific extension (and I have disabled called waiting on that extension) it WILL RING BUSY if the line is in use when that call comes in. The reason it will ring busy is because the PBX knows what DID was dialed and refuses to route the call to any other extension. I know that is probably crude … but am I understanding it correctly?

The Sales Rep is confused in his terminology (but hey, he’s a sales guy).

With and most other carriers, when you buy multiple ‘trunks’ you are simply buying a maximum number of “simultaneous channels” (or calls) that are allowed at any given time.

It’s very much like if you were buying a fractional PRI with 8 channels, where they give you use of up to 8 channels before your trunk is congested. (Where as the physical media can actually handle 23 channels and of course in the case of SIP, it’s “unlimited” only throttled by your available bandwidth.

The two “trunk” configurations that were provided to you by Bandwidth are for a Primary and Secondary trunk. All calls, fax or voice, will be delivered from the primary trunk unless it is down for some reason in which case they will be delivered to your secondary trunk. For outbound calls, you can simply put the primary trunk and secondary trunk in each route, so if for some reason the primary trunk was not accessibly, you would route calls through the secondary trunk.

Any call that comes in will come in with the DID that was dialed, on the “one” trunk. You must route the call based on the DID using the inbound routes. The format of the DID will depend on what you requested from and if the format for it and the CID is coming in an e164 format, you can either ask them to change it or you can just use the:


for your context in the trunk configurations (which you should verify is available in extensions.conf but should be. This will strip off the “+1” on the DID and CID, or for CIDs that have country codes other than +1, it will replace the +1 with “011” which is the standard US international dial prefix.

Anyhow - hope that helps and clarifies.