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Using the Internet without IPv4 connectivity

(jamesmcm.github.io)
296 points jmillikin | 2 comments | 29 Jun 25 08:23 UTC | HN request time: 0.742s | source
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simonjgreen ◴[29 Jun 25 09:20 UTC] No.44411529[source]▶
Slightly misleading title, this is more “getting to the IPv4 internet via an IPv6 tunnel through a VPS”. Also just called 4in6.

Interesting nonetheless!

We find at our ISP that if we break something with IPv4 we experience a very different type of support issue to if we break IPv6. Breaking v4 results in, broadly, a pretty hard “down” state. While folks are unhappy, it is at least simple. Breaking v6 results in weird, and a partial down, which manifests for the users as partial outages, slow starts due to fall back, etc. Especially if their gateways believe there is v6 when there isn’t.

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1. danappelxx ◴[29 Jun 25 10:26 UTC] No.44411884[source]▶
Mirrors my experience. IPv6 issues are frustratingly hard to triage and reproduce, lots of “works on my machine” etc.
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2. jeroenhd ◴[29 Jun 25 12:00 UTC] No.44412395[source]▶
I think it's because of all of those transition mechanisms and fallback code added over the years. IPv6 fails the same way IPv4 does, but because of the terrible bullshit ISPs do to IPv6 connections, you end up with tons of software triggering obscure timeouts and fallback mechanisms that lead to a system of almost working networking code.

If the absence of IPv6 would've been treated the same way absence of IPv4 is, troubleshooting would've become a lot clearer. In fact, it probably would've been easier because ISPs can't just ignore and disable ICMP on IPv6 so you can actually get a hunch where in the network the problem is rather than seeing traffic vanish into the void.