Validate setup with or without SBC

[andgasp]

Hello

We have an ISDN pri line at the remote location and are about to setup an SBC there to connect to the PBX via site-to-site vpn, along with 15 Ip phones with PoE.

We also have a new Patton E1 gateway to replace the current Avaya and to connect to the main site PBX, as per the article
https://www.3cx.com/voip-gateways/patton-sn4940-sn4950-sn4960/

I wonder, do I really need the SBC? Or better provision the phones with STUN?
How is the call flow established between the phones and the gateway, are calls going up and down the vpn once the call is established? Or is 3cx smart enough to avoid using the vpn for the remote phones calling outside?

Or is it better I configure the SBC with the public Ip and avoid the vpn? In this case as well the provisioned phones will directly use the Patton Gateway to make calls outside, skipping the SBC-PBX once the call is established?

Any alternative, considering we will on a later stage remove the Patton and use a sip trunk on the main site?

 

[SweetAction]

Always better to connect via SBC then STUN. However, since you have a site2site vpn, that's even better then SBC as phones are considered local to 3CX.

So, no, you don't need a SBC with a site2site VPN in place. Yes, all calls will travel over the s2s vpn (or sbc if you didn't have one) from the phone to 3CX server back to the patton. The phone will not use the patton directly in any situation - even if 3CX server was in the same site as the phones and the patton. Even if it was a sip trunk and not a patton pri converter.

 

[andgasp]

Thank you for the answer. So we are now considering putting the 3cx pbx on the remote site to avoid too much vpn traffic, and later move it to the main site. So we'll leave the sbc out of the equation. In this way we will register the phones with the pbx with the fqdn (split dns), and when we move it to the main site we won't need to reprovision the phones, but they will then cross the vpn.
At that point also get rid of the Patton gateway by registering the branch number on a sip trunk in the main site.
I think too many call legs would be created per every call otherwise, and troubleshooting would be far too complicated. Not to mention possible performance issues. Does it look like a valid plan?
Thanks

 

[SweetAction]

Sounds like a valid setup to me, also if you already have 3CX at the main site and want to do this, you could also do another 3CX pbx at the remote site and do bridging between the 2.

I personally don't think the first setup has too many call legs, but that's subjective and I can totally agree less is simpler for troubleshooting and performance reasons.