What router interface do I order from ATT?

Getting fiber from ATT and it’s cheaper if we get it bundled with voice. They require a PBX on our end so I figured that we would use Asterisk and softphones to fulfill the req.

They offer 3 choices:

  1. TDM Digital PRI (Primary Rate Interface) Phone system must emulate NI2 or 5E protocol for PRI.
  2. TDM CAS (Channel Associated Signaling)
  3. IP PBX

We will run Asterisk on Mac OSX or a linux box and just forward everything to our existing hosted, virtual PBX.

What should I order?


If the hosted system is SIP, and you just want to route to it, rather than replace it with Asterisk, I would say that Asterisk was a serious overkill, and that SIP would be the cheapest solution.

However, what you haven’t told us may change the decision completely.

Thanks David,

I’m having trouble getting a straight answer from ATT, but I think that they require that we have the incoming line physically connected to something here. I don’t want to buy a physical PBX that we will not use, so I figured Asterisk would be the cheapest easiest solution.

Our hosted virtual PBX is RingCentral (recently bought by ATT, but that’s no help). we currently have no phone lines on the premises. RingCentral routes calls to our phone number to all of our individual mobiles.

Does that help?


I’ve never heard of anyone getting a PRI to a site so that they can feed the trunk out to a hosted virtual PBX. Why not just order DID’s directly from Ring Central if you’re already happy with the quality of service from their servers to your location?

If you have digital line brought to your location you’ll be much happier running a PBX locally then take the double hit on your internet bandwidth to send the audio to your hosted provider and then back to your individual stations in your office.

I must be missing something.

We are a SaaS provider going live with our service in a couple of months. Our servers are on site. We have had ethernet over copper for development and beta. We are now getting fiber as our primary and will use the existing service for backup.

We just wanted fiber from ATT - no phone service. However, if we get the fiber bundled with voice it is much cheaper - so what the hell. However, ATT insists that we connect this voice service to a PBX - not sure why. So I figure:
Hook it up to Astericks
In case ATT or anyone tries to reach us on the number, just have Astericks forward all calls to our RingCentral number.

I’m tired of asking ATT why and not getting an answer that makes any sense, so if I can just comply that seems easier. In order to comply with Astericks (assuming that’s acceptable) I want to make sure that I ask for the right thing from them.

Is it making any more sense?


Ahhh, yes. Then, if the price is all the same, I think I would probably order a PRI from ATT. If the price is not the same, since you do not plan to use it, I would go with whatever is cheaper. If you have access to an inexpensive T1 card and old server you can make your own gateway.

If you do not have a server / card sitting around, I would recommend picking up prepackaged SIP gateway. The ones I’m most familiar with are the ones from Digium like the G100. Then you can configure the gateway register as an endpoint at Ring Central, to take all inbound calls on the PRI, strip the DID, and forward the call out to a number at Ring Central and block all calls from Ring Central.

Thanks…and sorry for my lack of technical knowledge in this area.

Our sales rep says that we get an ethernet connection with a T1/PRI handoff or SIP handoff.

If they can give us a SIP handoff can’t we just plug it into a Mac or Linux with Asterisk installed?

Not sure why SIP isn’t mentioned at all in our options???

Thanks again!

I would imagine that yeah, if they can link via SIP, then you should just be able to configure an Asterisk server running on a local machine to terminate it. So that’s even better.