For security reasons, we use VPN access to private IP addresses using OpenVPN.
Most customers at one point want access to their devices and may have used static IP addresses in the past. Security is a high priority for us and we therefore don't use public IP addresses for any of our sims. You still have access to them through a VPN, but the IP addresses remain private.
SIM IP address remain the same throughout the life cycle of the SIM. This means, no matter what network you connect to, you can access the SIM directly through the VPN using the same IP address.
For more information: