What are IP address ranges?

An IP address is a numerical label assigned to every device connected to a network. Not all IP addresses are treated equally — certain blocks are reserved for specific purposes defined by the Internet Assigned Numbers Authority (IANA) and documented in various RFCs. These reserved ranges include private networks (used inside homes and offices), loopback addresses (used for local testing), link-local addresses (automatically assigned when no DHCP is available), documentation ranges, and multicast groups.

Understanding which range an IP address belongs to is essential for network troubleshooting, security analysis, and firewall configuration. A public IP address is routable on the internet, while a private or reserved address is not and serves a specific local or administrative purpose.

Tool description

This tool checks an IPv4 or IPv6 address and identifies which IANA-defined range it belongs to. It displays the address classification, the CIDR block it falls within, its purpose, the relevant RFC, and whether the address is public or reserved.

Features

  • IPv4 and IPv6 support: Works with both address families.
  • Range classification: Identifies private, loopback, link-local, CGNAT, documentation, multicast, broadcast, and public ranges.
  • RFC reference: Shows the RFC that defines the matched range.
  • CIDR notation: Displays the exact CIDR block the address belongs to.
  • Public vs. reserved indicator: Clearly flags whether the address is routable on the public internet.

Supported address classifications

Classification Example range Purpose
Private (Class A) 10.0.0.0/8 RFC 1918 private networks
Private (Class B) 172.16.0.0/12 RFC 1918 private networks
Private (Class C) 192.168.0.0/16 RFC 1918 private networks
Loopback 127.0.0.0/8 Local host communications
Link-Local (APIPA) 169.254.0.0/16 Auto-configured when no DHCP
CGNAT 100.64.0.0/10 Carrier-Grade NAT (RFC 6598)
Documentation 192.0.2.0/24 Examples and documentation
Multicast 224.0.0.0/4 One-to-many delivery
Public — Routable on the internet

Use cases

  • Network debugging: Quickly determine whether an IP address seen in logs is internal or external and what its intended purpose is.
  • Security analysis: Identify unexpected private or reserved addresses in traffic that should only carry public IPs.
  • Firewall and ACL configuration: Verify address ranges when writing rules that need to distinguish between public and private IP space.