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How NAT traversal works (2020)

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Resurfaced independently across 3 calendar years, with breakout response in 3 of them.

submissions
7
submitters
7
observed span
2020–2023
peak thread · 106 comments
351 pts
latest 20+ return · 2023-08-02
305 pts

Submission timeline

2007–2026

One slot for every year since HN launched. Height is that year's peak points; orange marks a 100+ point or 50+ comment breakout. Select a bar to open its strongest thread.

First comments on top threads

HN comment order

I submitted this because it is the best summary of NAT I have read, and it goes into some of the technical details. Kudos to tailscale for writing this.

robocat·351-point thread·

> (NATs do not enhance security in any meaningful way, but that’s a rant for another time.) Eh, I'm not sure I agree. People plug all kinds of weird and wonderful crap into their home networks, they turn off their Windows firewall and allow connections to RPC ports, all sorts of nonsense. The main factor that prevents even more stuff being exposed to the internet than now (and there's a lot exposed already) is the prevalence of IPv4 NAT devices…

The article (like many others) distinguish between easy NAT (endpoint-independent) and hard NAT (endpoint-dependent symmetric NAT), but does not discuss how real-world NAT devices behave (whether they are predominantly easy NATs or hard NATs). In reality, home routers are generally Linux-based and share netfilter NAT implementation. And how this implementation behaves? Well, it is a symmetric NAT masquerading as a port-restricted cone NAT. While it is symmetric NAT, it tries to reuse internal port as external…

Discovered via a shoutout from hole punch video https://www.youtube.com/live/nuK_PqvTQxo?feature=share Dupe: https://news.ycombinator.com/item?id=30719137

yonz·1-point thread·

The first top-level comment from each of the four biggest threads, in HN’s own order. Excerpts are shortened; open a comment for full context.

Breakout years
3

100+ points or 50+ comments

Total points
846

reference only — not used in Hall rules or ranking

Total comments
172

reference only — not used in Hall rules or ranking

Every submission

DateTitle as submittedByPointsComments
2020-08-21How NAT Traversal Workspsanford220
2020-08-22How NAT Traversal WorksFirst breakoutsigna1116228
2022-01-22How NAT Traversal Works in Tailscalemadacol20
2022-03-17How NAT traversal works (2020)Best threadrobocat35137
2022-03-18How NAT traversal works (In Tailscale)pcr91030330
2023-06-28Tail scale NAT traversal (2020)yonz11
2023-08-02How Nat Traversal WorksHall induction · Latest 20+ point returnpunnerud305106