NetComm 3G38WV-TS Product Overview page 31

FREQUENTLY ASKED QUESTIONS
Do I need a Public IP address?
Every device that is connected to the public internet
is assigned a unique number known as an Internet
Protocol (IP) address. The difference between a
private IP address and a public IP address is that
private IP addresses are reserved for private
networks, and public IP addresses provisions wireless
devices with publically routable IP addresses.
A public IP address enables your device for full, 2-
way network traffic and internet originated
communications can reach the device directly.
You will need a Public IP address if you want your
wirelessly connected devices to receive "inbound"
data traffic from any internet connected system.
Public IP APN can also be used to resolve connectivity
issues with certain VPN solutions.