Phones won't register after network outage

[Dansas]

Used 3CX Express with Google to build server. Provisioned 4 Yealink T48s phones using STUN. Service works great but after a network outage, the phones will not register. After rebooting the phones, they will try to register for a few minutes then report "Registration Failed." Factory resetting then auto provisioning all phones again worked for 2 but the other 2 phones still won't register, they will auto-provision ok but fail to register.

The office has a PFsense router and I've assigned unique SIP/RTP ports for each phone and forwarded those ranges to each phone.

Running a packet capture on both ends, I see:
Status: 407 Proxy Authentication Required (on 3cx end)
Status: 481 Call/Transaction Does Not Exist (on phone end)

Does anyone have advice on what else I should try?

 

[cobaltit]

Is your IP blacklisted on the 3CX instance?

 

[Dansas]

No, I have specifically white listed the office's static IP. I finally got them all registered by factory resetting all phones, clearing states on my firewall, rebooting PBX server then re-provisioning. I fear though this will happen again next time the network drops. I also just setup outbound NAT rules with static ports for my phone's IP's. Will test an outage this weekend sometime to see if it makes a difference.

 

[AWS2P]

As you already have 4 phones connected, the use of an SBC could be helpful for you.No more shenanigans with ports etc..for stun mode.

 

[Dansas]

Does SBC require me to purchase a signed certificate for my server?

 

[cobaltit]

Nope.

https://www.3cx.com/docs/3cx-tunnel-session-border-controller/