Technical Guide · Reviewed 1 November 2026 · Primary Sources: IETF RFC 1918, RFC 6598, RFC 4193
Public IP vs Private IP
Understand the difference between globally routable public IP addresses and RFC 1918 private LAN addresses, how Network Address Translation (NAT) bridges them, and why RFC 6598 shared CGNAT addresses exist.
Global Internet Scope
Public IP Address
- Assigned by: Your Internet Service Provider (from blocks delegated by APNIC/IRINN).
- Uniqueness: Globally unique on the public internet at any given time.
- Routability: Forwarded across global BGP internet backbone routers.
- Examples: 49.44.0.1, 122.160.0.1, 2405:200:1601::1.
Local Network (LAN) Scope
Private IP Address
- Assigned by: Your home Wi-Fi router, office switch, or cloud VPC DHCP server.
- Uniqueness: Unique only inside your local LAN; millions of homes use 192.168.1.1 simultaneously.
- Routability: Dropped by public internet routers; requires NAT to reach the internet.
- Examples: 192.168.1.15, 10.0.0.5, 172.16.0.10.
Reserved Private and Shared IPv4 Address Ranges (IETF Standards)
| CIDR Block | Address Range | Total IPs | Standard | Typical Usage |
|---|---|---|---|---|
| 10.0.0.0/8 | 10.0.0.0 – 10.255.255.255 | 16,777,216 | RFC 1918 | Enterprise networks, cloud VPCs, large campus LANs |
| 172.16.0.0/12 | 172.16.0.0 – 172.31.255.255 | 1,048,576 | RFC 1918 | Docker container bridges, corporate VPN subnets |
| 192.168.0.0/16 | 192.168.0.0 – 192.168.255.255 | 65,536 | RFC 1918 | Home Wi-Fi routers and FTTH ONTs (e.g. 192.168.1.0/24) |
| 100.64.0.0/10 | 100.64.0.0 – 100.127.255.255 | 4,194,304 | RFC 6598 | ISP Carrier-Grade NAT (CGNAT) between CPE and carrier core |
Why Your Router Status Page Often Differs from "What Is My IP"
If you log into your home router admin page (typically 192.168.1.1 or 192.168.29.1) and inspect the WAN IPv4 address, you might see an address beginning with 100.64.x.x or 10.x.x.x, while our What Is My IP tool shows a public address like 49.44.x.x.
This happens when your ISP uses Carrier-Grade NAT (CGNAT): your home router translates your phone's 192.168.1.x LAN address into a shared 100.64.x.x carrier address, and the ISP's core NAT gateway translates that into a public IPv4 address. You can classify any IP string immediately with our IP Address Validator or plan your LAN subnets with the Subnet Calculator.
Technical Specifications & Protocol Facts
Authoritative parameters, dimensions, and IETF RFC compliance
| Parameter / Dimension | Technical Specification | Standard / Authority |
|---|---|---|
| Canonical Document Scope | Public IP vs Private IP — Route /public-vs-private-ip | IPAddressLookup.in Technical Reference |
| Supported Address Families | IPv4 (32-bit dotted-decimal) & IPv6 (128-bit hexadecimal) | RFC 791 / RFC 8200 / RFC 5952 |
| Authoritative Registration Protocol | Registration Data Access Protocol (RDAP) via IANA Bootstrap | RFC 7480–7484 / RFC 9224 |
| Special-Purpose Range Classification | Private LAN (RFC 1918), Shared CGNAT 100.64.0.0/10 (RFC 6598), ULA (RFC 4193) | RFC 6890 IANA Registry |
Frequently Asked Questions
Concise answers verified against IANA, APNIC, and IETF protocol standards
What is the primary purpose of Public IP vs Private IP?
Compare globally routable public addresses with RFC 1918 LAN ranges and RFC 6598 CGNAT space. Every output on IPAddressLookup.in follows IETF RFC standards and cites primary RIR/IANA sources.
Are IP and network queries on this page logged or shared with advertisers?
No. IPAddressLookup.in operates on a strict data-minimization model with stateless query execution, short-lived caching (15 minutes max for upstream RDAP/DNS), and zero persistent user lookup history.
How often is the technical documentation on IPAddressLookup.in reviewed?
All protocol calculators, RFC citations, and Indian telecom notes are verified by the 2026-11-01 editorial and engineering review cycle.
Related Network Tools & Technical Guides
Contextual utilities and reference documentation verified for this workflow
Diagnostic & Calculation Utilities
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Inspect country/region, ASN, provider, special-range scope, and data provenance for any IPv4 or IPv6 address.
- IP Address Validator & Classifier
Verify syntactic validity and inspect whether an IP is globally routable or reserved in an IANA special-purpose block.
- Subnet Calculator
Calculate network address, broadcast, usable host range, wildcard mask, and 32-bit binary mask for /0 to /32.
- IPv4 Checker
Inspect the visitor IPv4 address observed by the server, octet breakdown, and RFC 1918 / RFC 6598 CGNAT status.
- IPv6 Checker
Inspect 128-bit IPv6 reachability, eight-hextet structure, compressed/expanded form, and Indian dual-stack context.
Public vs Private IP · Canonical: https://ipaddresslookup.in/public-vs-private-ip · Reviewed: 2026-11-01
Reviewer: IPAddressLookup.in Technical Network Utility Group · Stateless Privacy · Accuracy & Data Limits