I'm rather lucky in that my ISP recently started offering IPv6 (and somehow my workstation appears to be using it by as the default), but none of the other PC's on my network do. (Win11 change perhaps?)
> NAT devices are detected by observing a difference in the expected and actual checksum of the UDP packet that is returned as the part of the Original Datagram in the ICMP Time Exceeded message. If they differ then it indicates that a NAT device has modified the packet. This happens because the NAT device must recalculate the UDP checksum after modifying the packet (i.e. translating the source port) and so the checksum in the UDP packet that is nested in the ICMP error may not, depending on the device, match the original checksum.
[1] https://github.com/fujiapple852/trippy/releases/tag/0.11.0
But I'm not sure who will and how they will find this information useful. If anyone can think of a reason why CGNAT detection can be useful generally, I can pitch this to the engineers.
Furthermore, run
curl ipv4.icanhazip.com
[0] https://en.wikipedia.org/wiki/Carrier-grade_NAT#Shared_addre...
More interesting is windows 11 auto configuring ipv6. Does you pc have a public ipv6 address starting with 2:: or fe80:: link local address?
Quick ipv6 crash course. Instead of DHCPv4 (there is DHCPv6 but it's optional) being required for address configuations, ipv6 uses somting called Stateless address Autoconfiguration (SLAAC). Normaly your router sends out Router advertizments packets and this tells devices about the default gateway, public prefix, dns etc... and pc will generate a public ip of (64 bit public prefix):(64 bit random number).
It seems like Windows 10 and eariler will not do ipv6 unless your router advertises it.
TL;DR learning ipv6 is easier than disabling it at this point
There probably isn't an ISP that gives out *static* public IPv4 addresses for free, but any ISP that supports IPv4 without CGNAT will give out public IPv4 addresses by definition. The two I've used in the US (Frontier, now Ziply) certainly do.