Comment by xurukefi

I hate NAT with a passion. It's a terrible technology, whose disruptive nature has probably prevented any novelty on the transport layer. But this article is oversimplifying things.

It is well known that NAT is not meant for security and that NAT is not a firewall. But one cannot deny that it implicitly brings some "default" security to the table. With NAT it's basically impossible to screw you over because there is no meaningful practical way to allow inbound connections without the client explicitly defining them (port forwarding). With IPv6, you could have a lazy vendor that does not do any firewalling or a has a default allow policy or maybe buggy firewall. With NAT that is not possible. There is no lazy/buggy NAT implementation that allows inbound connections for your entire network, because it is technically not possible. When a NATting device receives a packet with a destination port that has not previously been opened by a client, it does not decide to drop this packet because of a decision by the vendor. It drops the packet because there is simply no other option due to the nature of NAT. That is what people mean when they talk about the inherent "security" of NAT.

Again, NAT is terrible. We need to finally get rid globally of IPv4 and all the NATting that comes with it. But let's keep it to the facts.