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IPv6 Internet Issues

For the second time in a few months, I’ve had a pretty annoying experience regarding computer networks:

I had internet access, but websites would take ages to load.

Turns out that there’s routers that just don’t support IPv6 at all.

But my OS always tries to establish an IPv6 connection first, backs off for a bit, and then falls back to IPv4, which then works.

So if:

  • websites take relatively long to resolve, but then load fast
  • but pings are fast ping github.com

You might want to check whether IPv6 works:

Terminal window
curl --verbose -4 github.com # should resolve
curl --verbose -6 github.com # should break if IPv6 is the issue

Then you need to somehow disable IPv6 to resolve those long loading times.

What worked on NixOS for me was the nuclear option—disabling IPv6 in the kernel: 

# in configuration.nix
config = {
  boot.kernelParams = [ "ipv6.disable=1" ];
}