Hosted instance – source IPs blocked during migration, not removable via admin console

[senb_spl]

Title:

Hi,

We're migrating from an on-premises 3CX to a 3CX hosted instance. During the migration our devices made repeated registration attempts using IP-based authentication, and two of our public source IPs got blocked (20 Oct 2026, around 12:20 and 12:25 CET).

We've switched to username/password authentication and paused all registration attempts until the block is lifted.

The IP blocklist in the admin console doesn't help: the addresses don't appear there. So we assume the block sits at the hosting infrastructure level. 3CX support redirected us to the forum.

Could 3CX staff:
1. Confirm whether the block is applied outside the instance?
2. Lift it, or point us to the right channel to request that?

We can share the instance FQDN and IP addresses privately.

Thanks!

 

[Alejandro_3CX]

Hi @senb_spl I couldn't locate an existing support ticket under your email address, FQDN, or key. To help us assist you, please submit a support ticket directly with us, or contact a local partner so they can open one on your behalf.

Thanks!

 

[bitn2]

That doesn't really make sense... Were the phones using the public IP of the hosted instance as their registrar? An IP block is always visible in the console; if you are still able to resolve the FQDN from that IP address, then there is no block in place. What is being used as an SBC? Or have the phones been configured as "router phones"?

 

[Claas Felix Beyersdorf]

For me it sounds like the phones were configured for local LAN which made sense as the PBX was on prem.

So I would guess no one has reconfigured the phones to work as router phones or use a new SBC.

This would also explain the problem as the phones would try to REGISTER directly via IP which is blocked.

So I think its a misunderstanding how phones have to be configured to work with an PBX hosted by 3CX