Comcast SIP trunk on premise

[stever]

We currently have a traditional PBX with a PRI supplied by Comcast. We are thinking of moving to 3CX on premise with Comcast providing SIP trunks that terminate on premise. The Comcast termination device would have an internal IP. Does anyone have experience with this setup? If not, do you think we would have any problems?

Pros:
1. Been happy with our Comcast PRI
2. Calls won't be traveling on the internet and will have Comcast QOS

Cons:
1. Not supported by 3CX
2. Limits us to on premise installation

Steve

 

[leejor]

Comcast supplies (or will supply) a PRI that will then terminate on a (3CX compatible) gateway, or Comcast also supplies the gateway?

 

[stever]

We would not longer have a PRI that terminates in house but rather a gateway type device that provides the SIP trunks. Their device (I think Adtran brand) would have an internal IP number that I would point my PBX toward.

 

[Sopock]

From this you can see that some NAT may be involved

https://www.3cx.com/community/threads/separate-network-connection-for-sip-trunk.51370/

 

[stever]

My understanding was that I didn't need a second NIC card. I thought the process would be to set up a generic SIP provider and point it toward the Comcast gateway.

 

[Sopock]

And that gateway is also used for internet?

 

[stever]

The "gateway" (I may have the wrong term for that) is only for the SIP trunks. I would put the IP (internal IP on same subnet as PBX server) of the gateway in the Trunk Details of the 3CX SIP trunk setup page.

 

[jvivona]

We just installed for a client with a similar scenario - although it was Charter, not Comcast. Their PBX has an address similar to 10.0.0.10 and the Charter gateway has an address of 10.0.0.11. Just add a generic SIP trunk with that IP as the gateway IP - we put the same address in for the proxy - but it's un-necessary. Charter uses an IP Based deliver - so they needed to know the PBX internal IP in advance - but that's easy.

We use a number of providers who don't have (or previously had, but no longer) a SIP template. We use the generic template and tweak the parameters as needed.

The customer with the local net gateway is super happy, call quality is comparable to the PRI.

 

[cobaltit]

No NAT involved. the ESG (as Comcast calls it) is given an IP address on the same subnet as your PBX. Here is the guide:

https://sharesync.serverdata.net/us/s/rGiE3KFpVRqRkMQip0NIbF0033d6c4

 

[stever]

That's good news. It sure seems like it is the way to go with on premise if you have concern about call quality or latency. Not sure if the SLA is as good for SIP as it is for PRI, but our PRI has only gone down once in the last two years and that was only for 1.5 hours.

 

[cobaltit]

The service delivered should be identical as far as reliability. Effectively all you are changing in the current call path is the PRI gateway getting replaced with the ESG.

 

[[email protected]]

Comcast will provide (usually) an adtran. Your enterprise manager will give you a form to fill out with the internal IP of your 3CX and what IP you would like the adtran to be (in the same subnet). That adtran IP will become the IP you connect to.

3CX is fully supported by Comcast. There is a full tested solution with sample setup for 15.x.

Here is the TekVision certification testing and sample configuration file. (3rd party SIP certification testing company)

 

[stever]

Thanks everyone for the good information! Gives me confidence that we are going in the right direction.