I’ve made this observation on my own system, and confirmed with a customer’s system as well.
A remote worker with Polycom phone (IP601, VVX 400 confirmed, but others seen as well) connects from his AT&T Uverse home ISP to an Asterisk PBX (hosted or in company’s office).
The phone shows (sip show peers) as registered with the user’s public (Uverse) IP address.
The PBX admin issues "sip notify polycom-check-config " - but instead of the phone connecting to the PBXs FTP server and downloading its config files the home user’s Uverse router reboots.
I’ve tested this numerous times - with consistent results: As long as the remote user had AT&T Uverse it would reboot the modem.
I know that the Uverse router can also handle SIP connections, but I have no idea why it would respond to this specific command. Anyone else?