I have a VoIP extension that keeps trying to register with my IPO 500v.2 9.1.2.0 in Toronto. We don't have an extension setup with this Extension number. The VoiP client IP address is in Europe. Does anyone know how to block a specific extension from trying to register with IPO?

The better question to ask, is why are the ports opened? For someone to try and hit your system, it sounds like the SIP ports are opened allowing someone to try and authenticate a connection.

For what reason is the port opened up? If not a good reason, closing it would be easier...

Make sure that your system is secure. Auto create turned off etc....