[johannes1234321]

> > - What happens if my ISP decides to change my prefix ? How do my routing rules need to change? I have no idea. > > What happens if your ISP changes your IPv4 address?

To my internal net: nothing. All my internal addresses stay the same. All my firewall settings remain the same. Just to the outside world I come from elsewhere (which is good for my privacy, not sufficient obviously, though)

However if my IPv6 prefix changes all my IP based access control, which is a layer I use to limit what Internet of Shit devices can do, breaks. I could go to fe80 addresses for my local network, but those won't work across different network segments.

[brewmarche]

You should use unique local addresses (ULAs, fc00::/7) not link-local addresses (fe80::/10) for this. Choose a random prefix and advertise it in your network (you can use some website like https://www.unique-local-ipv6.com if you want).

This prevents clashing subnets when using VPN like it sometimes happens with IPv4.