SIP Dedicated Trunk Application for S-Series VoIP PBX


In some cases, client might have a dedicated SIP trunk from the provider. This kind of SIP trunk usually offers a dedicated cable to be connected with which comes from a specific ISP router, and exclusive for voice only without Internet access function. So what's the plan?

Regarding to S-Series VoIP PBX, there are 3 points noted:

  • Network interface should be configured as Dual Mode: One is for the SIP dedicated trunk. The other one is for local network and Internet access
  • Static Routes and Default Network Interface should be configured well. The SIP dedicated trunk data goes through the interface that it connects, and the rest data goes through the other interface.
  • If SIP remote extension solution is involved, the NAT settings should be taken into consideration. This is to avoid one-way problem.


Network Information Gathering

Here we have a sample for dummy use.

Local network IP address:, Gateway:
SIP Trunk SIP trunk IP address & port:; Interface IP address:, Gateway IP address:
Public IP IP address:


  • The Local network depends on your own planning. It is the local network that the PBX is deployed.
  • SIP Trunk IP address information was offered by the SIP trunk provider. Usually includes the interface IP address & gateway IP address, SIP trunk IP address & port.
  • Public IP is the public IP address that the remote extension registers to.

Simple Topology


Settings on the web interface

1. Network Settings

NetworkSetting.png2. Add Static Route for the SIP trunk


Route table review


3. If remote extension solution is involved, please proceed.



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