No ringback when bridging calls to downstream PBX

[Herbert Whistlefjord]

I am using inbound routes with a regex to catch the destination number and then bridge the call to a downstream PBX, like this:

action

bridge

sofia/internal/$1@172.18.20.5

I have found that there is no ringback in this scenario. I just get silence from the outside, then it works once answered.

Early Media | FreeSWITCH Documentation

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I tried adding {ignore_early_media=ring_ready} before sofia/internal/$1 but this doesn't make any difference.

I have done this type of deployment many times before without encountering this issue. Outbound calls do have working ringback but that may be generated by the downstream PBX.
Any ideas?

 

[Herbert Whistlefjord]

I have passed this to the carrier as a SIP trunk from them on a different SBC cluster behaves as expected, with an identical configuration. So pretty sure this is their issue.

 

[Herbert Whistlefjord]

Was all working Monday morning after they told me they couldn't see anything wrong. I'm blaming the carrier!