No audio when calling trunk on the same system

Hey there! I have three trunks configured on my pbx. When calling them from external numbers, they all work perfectly fine. Calling other extensions internally also works flawlessly. But whenever I try to call one of our external numbers from an internal extension there’s no audio. Phones ring normally, you can pick up the call, but on no side can you hear anything. Any idea why this is happening?

There are several possible causes for this issue; most trunking providers handle on-net calls specially, bypassing their media servers. Most commonly, it’s because your PBX is behind a NAT that doesn’t handle ‘hairpinning’ properly.

The simplest fixes avoid the trunking provider for these calls:

However, it’s possible that your issue is something other than hairpinning, and calls to or from other users of the same trunking provider will fail. I recommend that you test to confirm that this is not the case, before implementing one of the easy fixes.

They do? In my 15+ years of being at providers we never did that. On-Net means it stayed on our network and we didn’t pass the call off to the PSTN. That didn’t mean we would bypass important things like media servers. Why would you control the media that goes to the PSTN but not on your own network?

Now places like Vitelity, etc. that are aggregates generally don’t do On-Net routing because they always pass the media through from you (their end user) to what ever termination carrier they use for the call. They need the other side to do the media so they don’t do On-Net routing.

Because you’re basically saying that if it’s On-Net the provider is doing direct media between the two end user endpoints (which both could be behind NAT) and that’s just a really, really, really bad way to do things.

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