What Is an ISP Network IP? Home Broadband vs Corporate Dedicated Line vs CGNAT
What Is an ISP Network IP
An ISP network IP (broadband IP) is a public IP address assigned by an Internet Service Provider (ISP) — such as China Telecom, China Unicom or China Mobile — to a home broadband user or corporate dedicated-line user. Each time you go online, your router is allocated an IP from the ISP's address pool, and that is the address the outside world sees.
Home Broadband IP Characteristics
- Usually dynamically assigned: the IP may change each time you redial or restart the router.
- May go through CGNAT (Carrier-Grade NAT): multiple homes share one public IP — the outside cannot distinguish individual users.
- Limited geolocation accuracy: IP geolocation typically pins to the user's city or district (±10-100 km).
- High risk-control value: a home broadband IP means the visitor is a real individual user — more trustworthy than datacenter or proxy IPs.
Corporate Dedicated Line vs Home Broadband
| Item | Home Broadband IP | Corporate Dedicated Line IP |
|---|---|---|
| Assigned to | Home users | Enterprises / institutions |
| IP changes | Usually dynamic, may change | Usually static and fixed |
| Bandwidth | 100 Mbps – 1 Gbps shared | 10 Mbps – 10 Gbps guaranteed |
| Cost | Tens of RMB / month | Hundreds to tens of thousands RMB / month |
| CGNAT | Some go through CGNAT | Usually no CGNAT, dedicated public IP |
| Reverse DNS | Usually no PTR record | Usually has properly configured PTR |
CGNAT: Multiple Users Sharing One Public IP
As IPv4 addresses run out, ISPs widely deploy CGNAT (Carrier-Grade NAT) so that multiple home users share one public IPv4 address. This means:
- The externally visible IP may represent multiple real users simultaneously — blocking it affects all of them.
- Geolocation accuracy drops further — the IP may point to the ISP's regional node, not the user's actual location.
- The specific user cannot be traced back through the IP alone; ISP logs are required.
CGNAT address ranges are typically 100.64.0.0/10 (RFC 6598) or ISP-private 10.x / 172.x / 192.168.x subnets; if these appear in a public IP lookup result, the user is behind CGNAT.
FAQ
- Q: How do I know if my IP is behind CGNAT? A: Log into your router to check the WAN IP, then visit tmpip.com to see your public IP — if the two differ (WAN is 10.x or 100.64.x), you're behind CGNAT.
- Q: Is a home broadband IP permanent? A: Most home IPs are dynamic and may change on redial; some ISPs offer a "fixed home IP" add-on.
- Q: Is a corporate dedicated line more secure than home broadband? A: Corporate lines have dedicated public IPs, reverse DNS and SLA guarantees — better for businesses needing IP trust. But actual security depends on the enterprise's own measures.