What is the CGNAT IP range 100.64.0.0/10?
If your router's WAN address is between 100.64.0.0 and 100.127.255.255, you're almost certainly behind carrier-grade NAT. That range is reserved for shared ISP addressing in RFC 6598.
The range, in plain English
100.64.0.0/10 means every IPv4 address from 100.64.0.0 through 100.127.255.255. IANA set it aside so ISPs can give customers private-ish addresses inside the carrier network and share a smaller pool of real public IPv4 addresses. Your devices talk to the ISP; the ISP translates to a public address for the rest of the internet. That's CGNAT.
How to spot it on your router
- Open your gateway or router status page (WAN / Internet / Broadband).
- Write down the IPv4 address.
- If it starts with
100.64.through100.127., that's the CGNAT shared space. - Confirm with the CGNAT checker: your public IPv4 will be different from the WAN address.
Full walkthrough: How to tell if you're behind CGNAT.
What it means for self-hosting
- Inbound IPv4 (port forwarding, hosting a service from home) doesn't reach you on that shared address.
- Your ISP may offer a free opt-out, a paid public/static IP, or neither. Check your ISP page or the public IP guides.
- Sharing one public IPv4 with other customers can also mean extra CAPTCHAs and IP blocks: why that happens.
- CGNAT is an IPv4 problem. A public IPv6 (if your ISP gives one) can still accept inbound connections over IPv6.
Related private ranges
Addresses starting with 10., 192.168., or 172.16.–172.31. are the older private ranges (RFC 1918). They can also mean another NAT in front of you (including some CGNAT deployments). Always compare WAN vs public IP; don't guess from the first octet alone.
This site sticks to ISP facts. It doesn't review or recommend third-party products or services.