FreePBX PJSIP Trunk with no reg or auth

Hi everyone,
I have a few questions about this type of configuration.

I have successfully set up a PJSIP trunk between FreePBX and a PATTON SN4114. Everything is now working fine, but I don’t fully understand WHY these specific settings below made it work.

My Setup:

PATTON SN4114

  • No registration
  • No authentication
  • All calls are simply pointed to IP address 10.0.0.5 (IP of FreePBX)

FreePBX PJSIP Trunk Settings (via GUI):

  • Trunk Name: PATTON_analog
  • Authentication: None
  • Registration: None
  • SIP Server: 10.0.0.6 (IP of PATTON)
  • SIP Server Port: 5060
  • Outbound Proxy: sip:10.0.0.6\;lr
  • Contact User: 123111444
  • Match (Permit): 10.0.0.6
  • (All other parameters are default.)

What I Observed:

  • Without Match (Permit: 10.0.0.6), FreePBX rejects incoming calls from Patton with 401 Unauthorized. Since Patton does not support authentication, it never retries with credentials, and the call fails.
  • Without Outbound Proxy (sip:10.0.0.6;lr), FreePBX marks the trunk as Unavailable, preventing any outbound calls.

These two settings together make everything work, but I’m trying to understand WHY.

My Questions:

  1. Doesn’t “SIP Server” already define where the trunk should send traffic? Why is Match (Permit) also needed for incoming calls?
  2. Why does the trunk become “Unavailable” without Outbound Proxy? Shouldn’t FreePBX still be able to send outbound calls to the SIP Server?
  3. What exactly does “Match (Permit)” do internally in PJSIP? I assumed it only controlled which IPs are allowed, but it seems to also determine whether the trunk accepts incoming calls.

Thanks in advance for any insights