NAT also is known as Network Address Translation, is a service a modem provides so all of your devices will work off a singular external IP by giving them internet IP's Such as 192.168.1.2
What is Double NAT?
Double NAT is when 2 devices on your network have created an internal IP address for you.
Why has this happened?
By not having a Static IP address you are adding an extra layer of security being protected with an internal IP as shown in the diagrams below.
Compared to a Gamer pack Customer
You will notice that the MyRepublic Network no longer is handing out an IP address
Types of NAT
There are 3 types of NAT Strict, Moderate, and Open.
My NAT is strict why and how do I fix this?
Nat becomes strict when the ports required for that game or server are closed this can be changed by forwarding the ports required in your router to the device needed them.