SIP typically uses UDP ports 5060 and 5061 so a scan will not show it as open. I don't know how these guys find an open SIP server, but they do. Non-stop SIP invites and registrations. Toshiba is pretty good about not letting these get through, but they don't stop

MIPU IP has never worked with NAT. If you have public-facing phones the MIPU must always have a dedicated public IP address assigned to it. There are a lot of technical reasons why, but it is a bit much to go into details. You can get SIP to work on an MIPU with a router that supports SIP ALG, but routers do not understand the Toshiba IP protocol. Sometimes they think it is H.323.

Other routers will probably also work, but I think Toshiba mentioned this brand because it was a lower-cost solution. Back in Toshiba many years ago class they used a Sonicwall

Check PM.

Edit: I should note that a VPN from the user's premise will also work if you wanted to keep the card internal.

Last edited by newtecky; 02/23/22 11:35 PM. Reason: Add VPN comment