CGNAT

Carrier-grade NAT is the internet's answer to running out of IPv4. Rather than give each customer a public address, a provider hands out private ones internally and translates them all through a small set of shared public addresses. Dozens or hundreds of households can sit behind a single visible IP.

This quietly reshapes what an address means. When many real users share one public IP, that address cannot identify a person, and blocking it punishes everyone behind it, which is precisely why mobile networks, where CGNAT is near-universal, produce such trusted proxy addresses.

It also explains why some residential IPv4 is a shared, contended thing rather than a clean one-per-home address. In markets that lean hard on CGNAT, the residential address you route through may be carrying a crowd, which is a fact worth knowing before you assume one IP equals one identity.