No audio when external call gets forwarded to another external number

Dealing with some odd issue… Any suggestions would be much appreciated.
FreePBX 14 (installed from image) is sitting behind firewall (remote office). SIP trunks are registered to external Asterisk box (sitting on public IP, access limited through IPTables, this is “main” office). Asterisk is configured as a peer with provider.

Here is the issue:

  1. External call arrives to Asterisk and gets forwarded to FreePBX.
  2. Depending on condition, calls gets forwarded to a cell phone (or another external land line)
  3. external phone rings but when answered - no audio is coming through

Calling from internal number to external number - no issue…
call from external to internal extension - no issue…
call from external to internal extension that was answered and then manually transferred to external number (attended transfer) - works…
but call from external number that gets automatically forwarded to another external number - does not work

Setup use to work with version 13 of FreePBX… but when we did a fresh install of 14 - does not work…
canreinvite is set to no, NAT is set to yes (rport,comedia)…
If I move FreePBX from behind the firewall to public site (obviously adjusting nat=no plus some other obvious settings especially for extensions) - works fine…

It is gotta be something simple that I am missing… Any pointers would be greatly appreciated.


In your router/firewall, forward the RTP port range (default UDP 10000-20000) to the PBX.
Or, set up some way to send audio from Asterisk prior to the cell being answered.

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