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Comment by monocasa | Hacker News Reader

That's not true, at least for xbox live. It's NAT punching will gladly use UPnP if available, but doesn't rely on it, even for multiple devices on the same public IP.

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It's unlikely that you will have an "OPEN NAT" status on more than one console without UPnP at the same time.

Depending on the game you're playing, that may or may not be an issue.

It can stop you connecting to certain players in a peer to peer scenario.

It'll be fine. They'll be on two pretty arbitrary public ports, but it works just fine if you have a vaguely sane nat implementation in your router. That's the whole point of nat punching. And even if you have an incredibly broken nat implementation that won't accept UDP packets from other sources than the server you originally connected to, there's a fallback pathway at the first layer of that port 3074 protocol that bridges p2p messages through live's backend.

As another example, last time I checked WebRTC didn't use UPnP, but has all the same issues as a fundamentally P2P UDP protocol. They use STUN/ICE/TURN, live uses custom protocols filling the same niches.

This Xbox help article explains how having a "Moderate" or "Strict" NAT can affect you and how it can be solved:

https://support.xbox.com/en-GB/help/hardware-network/connect...

I don't think anything has fundamentally changed in this area since the days of the Xbox 360. Back then it was a PITA to get two or more consoles working properly without UPnP, and I can't see anything about the problem that would be different now.

Nintendo has a similar page:

https://www.nintendo.co.uk/Support/Nintendo-Switch/Troublesh...

So does Sony:

https://manuals.playstation.net/document/gb/ps4/settings/nw_...

I hate Sony for that page. I’ve helped multiple people with router issues who turned out to have forwarded all those ports from wan to their PlayStation (or it’s previous IP). Ofc it wasn’t the issue at hand, but horrible none the less.

How does it work with IPv6-only networks?

The last I looked on PS4, they expected you to use a particular port. I don't think there was a dynamic portion, just forward port X to the PS4. I could absolutely be wrong though, it's been a while.

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