SBC Extension and BLF limitation

[stever]

We are planning a 3CX cloud installation. We have four sites with the expected extensions at each site being 60, 15, 4, and 4. SBC specs say 50 extensions and 250 BLF's are the max. Our main location will exceed both of those maximums. Assuming those specs are up to date, what options do we have? Are we better off putting the system on premise with SBC's at the smaller sites?

Specs: https://www.3cx.com/blog/docs/session-border-controller-comparison/

Thanks,
Steve

 

[sip.bg]

Can't you this with VPNs or MPLS ? You may experience limitations using SBCs.
If you don't need local survivability in remote locations, e.g. having local trunks and local connectivity, etc., you can handle it with one PBX (cloud based).

 

[stever]

I want to avoid dedicated circuits (MPLS). Do you mean to have a VPN between our corporate firewall and the VPS hosting the 3CX server?

I am using a VPS server from OVH for the 3CX. System works great, good clarity, low latency, IP Phones and soft phones are good. I have read though that without a SBC, I will have sound issues as more extensions are added. We also do a bit of extension to extension calling, so the SBC would help out there.

Everything I have read says that I need to have an SBC with cloud installation but SBC will not handle our main site.

 

[sip.bg]

If using OVH or other third-party cloud, you may need to use 3CX SBC, as probably you won't be able to make VPNs, as you won't have access to cloud router setup. Typically VPNs must be organized between your PBX site and each of your remote sites.

If not using tunnel service like 3CX via SBCs or VPNs you may experience theoretically issues with audio or security problems, so it is recommended to use tunnels. This is not obligatory, as in almost 100% of the cases you can use remote phones configured with STUN (to register to PBX with correct public address: port). Still QoS is recommended to be implemented at your remote routers to ensure proper operation of remote phones.