Solved SIP Trunk Configuration

[rgd001]

Dear All,

I have a 3CX environment configured on local network 10.20.x.x with a dedicated public ip routed by the firewall (inbound/outbound) the system works fine just like any 3CX installation.
Our ISP provided us with a router where SIP trunk is configured using a private ip 10.206.8.74/29 connected to their sip register 41.x.x.x

Based on my ISP, I should use the 41.x.x.x to have SIP trunk registration, however that ip is mapped to connect to 10.206.8.74.

With the current installation, my 3CX will reach the 41.x.x.x using its public IP which cause registration failure.

My ISP wants me to use their private ip as my 3CX ip address which is not possible because the 3CX public services and local installed phones will not work.

I replaced my debian installation with a windows installion with 2 network cards 1 for my lan and 1 for the sip trunk. This configuration has an issue that I have 2 gateways. In my firewall I disabled outbound rule for testing. 3CX successfully registered on the sip trunk 41.x.x.x but the behavior of the calls is not right.

I am able to receive and send calls using the SIP trunk but the callee can't hear audio coming from my side while I cant hear him and I can hear a return of my audio when talking.

Please advise

 

[YiannisH_3CX]

Hi @rgd001

You will need to use the second NIC only for your trunk and remove its gateway. Then you will need to add static routes on the OS level to route traffic correctly through the NIC.
You will also need to instruct your trunk to use the second NIC's local IP in the contact and SDP.

So your primary NIC will have the local IP 10.20.x.x and will have a gateway. This NIC will be used to access the internet and connect local phones to the PBX.
The second NIC should have the IP 10.206.8.74 and should not have a default gateway configured. This will only be used for routing calls to your trunk by adding static routes.

I am assuming you are not using a supported provider but here is a guide of a similar setup from a supported provider.

 

[rgd001]

Hello,

Thank you alot!!!! this resolved my issue

Regards

 

[YiannisH_3CX]

Glad to see your issue has been resolved.