First of all, **What is NAT?**
Network Address Translation (NAT) is designed for IP address conservation. It enables private IP networks that use unregistered IP addresses to connect to the Internet. NAT operates on a router, usually connecting two networks together, and translates the private (not globally unique) addresses in the internal network into legal addresses, before packets are forwarded to another network.
As part of this capability, NAT can be configured to advertise only one address for the entire network to the outside world. This provides additional security by effectively hiding the entire internal network behind that address. NAT offers the dual functions of security and address conservation and is typically implemented in remote-access environments.
Basically, NAT allows a single device, such as a router, to act as an agent between the Internet (or public network) and a local network (or private network), which means that only a single unique IP address is required to represent an entire group of computers to anything outside their network.
Moving on, the 3 NAT types, when concerning gaming consoles/PCs, PS3/PS4, or the Xbox 360/Xbox One, are
- Open (Type 1)
- Moderate (Type 2) &
- Strict NAT (Type 3)
NAT1 is a direct connection to the internet; all ports are accessible, with no port forwarding rules required. Ultimately, an Open/Type 1 NAT will provide the best connection quality whereas Moderate and Strict NAT restrict the connections between a gaming console or PC. If your internet connection has a public IP address (non-RFC1918, non-RFC6598) on the exterior interface of your home router, you should be able to have your PS4 run in NAT2 mode. If you control the port forwarding on your home router, you should be able to get the PS4 to run in NAT1 mode, even on an internal RFC1918 address.
NAT2 is a single layer of public-to-private conversion, and requires assisted port forwarding to achieve inbound connections to the PS4. The Moderate, Type 2 NAT, as well as Strict, Type 3 NAT, limits the connections that can be created between your gaming console or PC and someone else’s gaming consoles or PCs. Users with Moderate NAT, or type 2 NAT, are only able to connect with other users also having a Moderate NAT type, type 2, or an Open NAT Type, type 1.
NAT3 is two layers of conversion, and usually involves a carrier-grade-NAT device at the ISP, as well as a NAT device at the home, making it nearly impossible to achieve direct inbound connections to the PS4; in NAT3 mode, only server-assisted connections are possible, with each PS4 establishing an outbound connection through the two layers of NAT devices, with centralized servers mediating the PS4-to-PS4 communication. Users with Strict/Type 3 NATs can only connect with other users using an Open/Type 1 NAT.Furthermore, at a smarter NAT 3 setup, If you see an address in 100.64.0.0/10 on the outside interface of your home router, you’re out of luck; you’re in NAT3 territory, may GOD have mercy on your gameplay 
More to come from the Mikrotik Side …
