What Is CGNAT? Carrier-Grade NAT Explained

Quick answer: CGNAT is NAT operated by an ISP, allowing many subscribers to share a smaller pool of public IPv4 addresses.

CGNAT vs home NAT

With ordinary home NAT, your router translates your devices to the public address assigned to your connection. With CGNAT, the ISP adds another translation layer upstream. Your router may therefore receive a shared or non-public WAN address while websites see a different public IPv4 address.

Why CGNAT matters

CGNAT can affect inbound connections, port forwarding, self-hosting and some gaming or remote-access setups. It is common on mobile and broadband networks because public IPv4 space is limited.

Compare your router’s WAN information with the address shown by WhatIP IP Lookup when troubleshooting.