Remote site with a local gateway

[sysadminmz]

As far as I understand, SBC is only used to connect back to the 3CX remote IP phones only.
However, given the following situation, how would you address it:
Main site with 3CX and PSTN gateway and SIP trunks.
Remote site with several IP phones.
However, there is a need for FXO gateway in the remote site as there is a particular line that can only be delivered on this site.
How would you make it work?

 

[VasilisV_3CX]

Hi @sysadminmz,

However, there is a need for FXO gateway in the remote site as there is a particular line that can only be delivered on this site.

What will that specific line be used for? Will this actually need to connect to the PBX or will it link to a standalone device?

 

[sysadminmz]

It will be used mostly for incoming and outgoing calls within the remote site.
There might be a need to route some incoming calls to phones registered directly to 3CX main site.
I am thinking something like this:
FXO line >>> Grandstream gxw4104 >>> SBC >>> Tunnel >>> 3CX
Phones behind SBC being able to make and receive calls from FXO line
Phones behind 3CX being able to make and receive calls from FXO line

 

[VasilisV_3CX]

Hi @sysadminmz,

I am thinking something like this:
FXO line >>> Grandstream gxw4104 >>> SBC >>> Tunnel >>> 3CX

This isn't supported. What you should do in this case is create a site-to-site VPN, and everything will appear local instead. You'll add both gateways to the PBX and all phones physically remote or otherwise, will appear logically local.

 

[sysadminmz]

The good thing though is site to site VPN is already in place.
Now I face a design scenario to choose:

1) main site with 3CX and remote with SBC with gateway connected to 3CX in the main site via VPN.

2) main site with 3CX and remote site with 3CX with gateway configured and connected through a bridge to main site 3CX.

If you ask me why like that? it is because the remote site still needs to be able to use the FXO line as well as use PSTN lines which are in the main site.

Note: There is no need to have presence exchanged. The only reason remote site needs to talk to main site is to use PSTN line.

What are your suggestions?

 

[VasilisV_3CX]

Hi @sysadminmz,

Given that you already have a site-to-site VPN established, everything within your remote network should appear local to your main office negating the need for a SBC or a second PBX. That said, since all of your FXOs will be logically local, they'll be able to use your PSTN lines.

 

[sysadminmz]

Hi @VasilisV_3CX,

The thing is E1 gateway is on main site and FXO gateway is on remote site.
Remote site needs to be able to use both gateways.
There is no need to exchange presence information between main and remote - the one thing needed is to share the gateways.
Another thing to consider using SBC was to ensure local traffic stays within the remote site and not traverse site to site VPN?

 

[leejor]

As mentioned, if the remote site is connected by VPN, then there should be no need for the SBC. All devices would be considered local to the main PBX if using VPN. This would include the PSTN gateway at the remote site. All sets, both at the remote site, and the main site would have access to all trunks ,depending on how you set up your outbound rules.

You could still use the SBC at the remote site, to keep local traffic local, but just connect the PSTN gateway using VPN.

 

[sysadminmz]

As mentioned, if the remote site is connected by VPN, then there should be no need for the SBC. All devices would be considered local to the main PBX if using VPN. This would include the PSTN gateway at the remote site. All sets, both at the remote site, and the main site would have access to all trunks ,depending on how you set up your outbound rules.

You could still use the SBC at the remote site, to keep local traffic local, but just connect the PSTN gateway using VPN.

The main reason for wanting to keep remote site traffic local is due to unable link causing the VPN to flap. That is why thought of SBC.
Additionally, little to none, the main site will have to use the gateway on the remote site, it will be mostly within the remote site.
There is flexibility to run another 3CX instance in the remote site, and I am just wondering what is the best design given this scenario.
The only reason remote site needs to talk to main site is to use the E1 gateway.

 

[leejor]

If the VPN is unstable, for some reason, then I can understand not wanting to use it even for the gateway alone. However, it might be an idea to figure out what the issue actually is, and fix it, rather than being resigned to the fact that you can't use it.

Installing a second 3CX at the remote site is certainly a possibility. You could then use a Bridge trunk for outbound calls using the trunks at the main site. You may require a prefix for extension to extension calls depending on the extension numbering range currently used at each site.

 

[sysadminmz]

Yes, actually it is not an issue with the actual VPN, but the link instead. It might take some time to get that fixed as overall the connectivity is unreliable.
I might go then with the bridge trunk approach, it would be ideal if SBC would support gateways registration.
Thanks.