Carrier-grade NAT address
100.64.0.0/10
100.64.0.0/10 is the shared address space ISPs use for carrier-grade NAT (RFC 6598). It isn't routed on the public internet, so there's nothing public to look up.
At a glance
- Block
- 100.64.0.0/10
- Defined in
- RFC 6598
- On the public internet
- No
About this block
There aren't enough public IPv4 addresses for every customer, so many ISPs give each customer's router an address from 100.64.0.0/10 and translate many customers to one public address at the edge of their network. This is carrier-grade NAT (CGNAT).
The block was set aside in 2012 so ISPs wouldn't have to borrow private ranges that their customers' own networks already use. Like a private address, it only means something inside one ISP's network.
Where you'll see it
- As your router's WAN or internet address. Your ISP uses CGNAT: you share a public address with other customers, so incoming connections and port forwarding won't reach you unless the ISP gives you a public address or you use IPv6.
- As the first or second hop of a traceroute, where your traffic meets the ISP's NAT gateway.
- On Tailscale, which gives each device an address from this block (100.x.y.z).