Force a trunk to use a specific interface for calls

I am adding a new provider to my PBX and they have dedicated line (RJ45) connected to my PBX box.

My current setup is I have 1 interface (this has internet connectivity and it is also the interface which all my phones communicate to). I am adding a second interface to my PBX so this new provider can connect its line to the PBX.

What I will be doing is adding a new interface with its corresponding IP/subnet etc. I can probably setup the new trunk simliar to my other trunks.

What I am not sure how to approach is how do I force all calls to use that specific interface while keeping my current interface (the one that has internet and phone connects to) in tact so my phones stay connected and I can receive updates through my current interface.

My new provider is finalizing the setup so I don’t have anything to test at the moment. I am just bringing up the question before I am jamming with time to migrate services over.


Set up a trunk that corresponds to the type and configuration your provider is giving you. The type and information will depend on the underlying technology.

Remember, just because the jack is an RJ-45, you might not be getting an Ethernet connection. You may be getting a PRI or T1, both of which are delivered on “network cabling”.

Once you have the trunk set up, you can set up outbound routes that correspond to several different methods for prioritizing your outbound connection through the trunk. It’s sometimes important to remind people that “trunks” and “outbound routes” are different and largely unrelated. Obviously, you need both, but they are largely independent and manage their own phases of an outbound call.

When you get details and if you have questions, let us know.

Just a note, if the signalling is “PRI or T1” then the “registered jack” will actually be an RJ48, they look the same but they are wired differently, if after physically connecting the external device to the servers ethernet port, then :-

ethtool ethn # (use the appropriate n)

will see if the physical link is up., if it is then assume RJ45 and configure your appropriate ethn as needed, don’t set a gateway on it, but setup your trunk’s “host” to that ip.

Thanks for the heads ups. I am still waiting on their setup to finalize before I can start testing. I am just trying to jump into the question now to prepare myself so there wouldn’t be too much delay when I am doing the actual test.