As many of you probably do, I use Vonage service at my home over my cable Internet connection. The other night as I was sitting downstairs trying to convince my 1 month old to go to bed when I began to wonder, “how does Vonage manage to make it so easy to connect my home phone to their service?”. I was especially curious when I considered that no router changes on my home network have ever been necessary. I just plugged in the magic ATA device they sent me and the phone just worked. Then, of course, I couldn’t help but think, “wouldn’t it be great if my home phone was connected to my 3CX system at the office? Then I wouldn’t have to pay Vonage at all and I could use all the great features of 3CX”. That was all it took, I had to figure this out. So, I set out on a quest to connect my home phone to my corporate 3CX system with the requirement that it had to work just as “magically” as Vonage.
And let me spoil this post by telling you that 3CX did not fail to impress me!
As many of you know, using remote phones without VPN is all over the 3CX forums. It’s one of the hottest topics out there. NAT and firewalls often create complexities in making this work easily and end up requiring router and firewall modifcations. Since this is really the same thing (with the additional complication of not using a true IP phone but rather an ATA adapter with my home phone) I figured I was out for some trouble on this. But, hey, I’m a gluten for punishment!
I began by choosing an ATA adapter. I wanted it to be inexpensive, like what you get with Vonage (in the $50 range). So, I chose the Linksys PAP2T-NA. It’s a simple 2 port FXS ATA device with 1 ethernet connection to plug into my home LAN. I ordered one online and had it in a few days. This device is actually used by many service providers so I was feeling good (as much as possible anyway) about the possibilities.
Once I got the device and began surfing around the admin interface, I was extremely impressed with the amount of specialized NAT handling for SIP/RTP that this device had. I actually found it to be more rich in this area than many (if not all) of the IP phones I have used. But would 3CX interoperate with these more advanced NAT handling features such as SIP keep-alives? We would see…
So, I decided to start simple and take it step by step. I began by simply enabling STUN and NTP on the device and setting the registration and proxy servers to the external DNS name of my corporate 3CX system (note I already have UDP 5060 for SIP mapped into my PBX along with UDP 9000-9015 for audio). I popped up the admin interface to 3CX…and….nothing. No registration. OK, no problem, try again.
So, next, I went back to the STUN settings and enabled all of the VIA settings and then enabled NAT keep-alive with a setting of 60 seconds. I pulled up the 3CX admin interface…and….BAM…fully registered! “Great,” I thought to myself, “let’s try a phone call.” So, I called my desk phone at the office and it rang right through! But, when my voicemail picked up….no audio. But, hey, we got it registered, so that’s a start!
Then I decided to take a closer look at the FXS port settings page. I noticed that I did not have my global NAT preferences mapped against this FXS profile. So, I turned that mapping on and enabled NAT keep-alive for this particular FXS port. I picked up the phone, made a phone call….voila! It worked like a champ! Perfect audio in both directions.
And that was it. It’s been working great ever since without ever having to touch my home router. So, who needs Vonage when we have 3CX and a $50 linksys ATA adapter? Not me!
PS- If anyone wants details on the specifc options I enabled please feel free to post a comment and I will respond.