PR60x NAT

NAT Filtering.

Network Address Translation (NAT) determines how the router processes inbound traffic. Secured NAT protects computers on the LAN from attacks from the Internet, but might prevent some Internet games, point-to-point applications, or multimedia applications from working. Open NAT provides a much less secured firewall, but allows almost all Internet applications to work.

Know what: This is neither something technical, nor standardized in any way!

Now we want to solve the puzzle posed at the beginning - why should there be different NAT types? If you are ever asked by young people addicted to computer games which type of NAT needs to be set on the XBox or the router and you frantically look for the standardized description of “Open NAT” on the website https://tools.ietf.org/, “ Search for “Strict NAT” and “Moderate NAT” and don’t find them: this division into three “NAT types” is not a technical standard at all, but rather an invention by Microsoft. The game console manufacturer uses this distinction to define the different port forwarding techniques that are used for said online games.

The different NAT types:

Type 1, Open NAT: Any IT system on the Internet can establish connections to the ports and thus the PC in your network.
Type 2, Closed NAT: An IT system from the Internet can only establish a connection to the ports and the PC in your network if the local system has previously initiated the connection - the "classic" NAT and masquerading.
Type 3, Moderate NAT: Your router only forwards a specific IT system from the Internet to any port on your PC.

There are plenty of instructions on the Internet on how to set which NAT type on certain routers or game consoles - and online gamers are often overwhelmed trying to find the "right" settings for their system. On some websites it also says:

«Should I use UPnP, Port Forwarding, or both? Whenever possible, use UPnP. Port Forwarding should only be configured when you cannot use UPnP. It is not recommended to enable both UPnP and Port Forwarding at the same time.»

Said that much: Your Router is Type 3 - Closed NAT, but (of course) does allow you to configure port forwarding, so making it Type 3, Moderate NAT.

A discussion which does not exist in the business router class.

Where does the ISP come into this game? Not all Internet connections are exposed and reachable direct from the wild Internet. With the lack if available public IPv4 network subnets, ISPs started to deploy things like Carrier-Grade NAT. Here your router does not get a public IP address directly assigned, instead some deploy an IP address from the 100.64.0.0/10 network, very "cheap" ones deploy RFC 1918 Private Internet Addresses. In either way, it's not reachable from the wild Internet.

This does become a problem if people try to configure IPv4 NAT port forwarding on their routers, but no connection can -ever- be established successfully. This makes up the much bigger problem then these gamer theories from above.

And this is where a correct deployed IPv6 network (from your ISP) comes into play. Mind you: No more NAT, no protection, except if you have a good firewall allowing to configure IPv6 firewall rules. Now all IPv6 traffic can reach direct your whatever device you have connected to your network!