Hi George, thanks for the added information.
So - this config is inherently a bit of a challenge compared to a 'regular, simpler' deployment - I am not sure if you have possible option to seek support (ie, pay 3cx, or a partner) to help with moving this along. I did a bit more gentle digging via google search,
a few relevant hits pop up in the forums, for example
https://www.3cx.com/blog/docs/network-configurations-supported-3cx-phone-system/
and
Hi
I have seen the documentation about having 2 NIC's on a server and having 1 connected to the internet via ADSL and my VoIP provider lines connected through this connection.
The other NIC is connected to the customer internal LAN where a voice VLAN is created.
Can someone please explain in a bit more detail how to have this working proparly, I know windows complain about having 2 default gateways and I need to set 1 static route. What would the best way be to have this working?
Regards
Johan
the first link is focused on windows networking 3cx config but is still informative even if you have a linux-based 3cx instance, I believe
Broadly speaking I think your choices remain the same,
probably the simplest config
assuming your SIP carrier wants you to use their ISP service only for SIP traffic. And you have a different ISP at your site for normal internet traffic.
1) you need dual physical NIC in your 3cx instance, the primary NIC will have standard LAN config and default gateway to internet is on this interface. Then second NIC will be cabled directly to the device from VOIP_provider which gives an IP in their ISP/VLAN/network. And you need to tweak config in your 3cx related to your trunk, telling it to use the secondary NIC for this SIP traffic
or more fiddley, requires firewall expertise and being familiar with your firewall at your site
2) you have dual-wan on your firewall, both are active concurrently, primary WAN is with main-internet-ISP-service-provider and is default for all traffic. second-WAN interface is attached to the ISP_modem_Device and has access (only) to the SIP Trunk server. as a baseline you have this attached, and may successfully ping to the IP address or FQDN of the special SIP Trunk Server. If you can't get this in place as baseline, you are done/dead in the water. Once you have this in place, your second config task would be to put in place a specialized firewall rule which (more or less) must designate "Outbound traffic to SIP_SERVER which originates from (3cx_SERVER_LAN_IP_ADDRESS) must route out via WAN2 not WAN1. But to be honest this config is delicate and fiddley, your better path to success probably is to do this on your 3cx host (only) and not at all on your firewall.
In terms of testing (simpler route - option one) - all I can suggest as an initial validation step.
use a simple controlled test. For example, a laptop or desktop computer. With connection only to outside world via (Modem?Device your SIP trunk provider has given you) - I still don't know if this is a DSL unit or something else - end of the day it does not really matter. Your 'easy control test case' - you just *must* be able to get the link up to the VOIP_ISP network, and then ping successfully to their SIP server FQDN. Then take note of output from a 'traceroute' for reference, and write down some info about what your IP address is, just so you know. Optionally you can use some simple SIP_CLIENT agent software on your TEST_MACHINE to validate "hey can I actally make a SIP Connection from this device, to their SIP_SERVER with actual success?"
once you have this tested and working in a 'simplest use case' you are in a better position to believe you have maybe some chance of success in configuration of dual-interface settings on your 3cx instance / which can in theory do what you want with very careful attention to detail, reading the documentation, and proceeding carefully.
Tim
