Smart Web Apps Guide
Network tools

Network tools guide

Network tools help you answer: “What is my public IP?”, “What network does this IP belong to?”, and “Who manages this domain or address block?”. These are essential for troubleshooting, allowlists, and security reviews.

IP basics
  • IPv4 looks like 203.0.113.10.
  • IPv6 looks like 2001:db8::1.
  • Your public IP can change (dynamic IPs are common).

Tools to try

What’s My IP? IP Subnet Calculator WHOIS / RDAP Lookup Domain Availability Checker

Public IP vs private IP (why your router shows a different address)

Many home and office networks use NAT (Network Address Translation). Your device gets a private IP address inside the network, and your router uses a public IP address to talk to the internet.

Common private IPv4 ranges
  • 10.0.0.0/8 (10.x.x.x)
  • 172.16.0.0/12 (172.16.x.x – 172.31.x.x)
  • 192.168.0.0/16 (192.168.x.x)

The What’s My IP? tool reports the public IP seen by the internet. If you enable a VPN, the public IP often changes to the VPN exit address — that’s expected.

Subnetting in plain English

A CIDR prefix like /24 tells you how many bits describe the network. The remaining bits are host bits (the number of addresses). Smaller prefixes mean bigger networks (for example /16 is bigger than /24).

Quick intuition
  • /24 → 256 total addresses (typically 254 usable hosts).
  • /25 → half of a /24 (typically 126 usable hosts).
  • /30 → tiny subnet (typically 2 usable hosts).

Use the IP Subnet Calculator to derive the network address, broadcast address, mask, wildcard mask, and the usable host range.

RDAP vs WHOIS

RDAP is the newer, structured replacement for WHOIS. Some records are privacy-protected, and some registries redirect you to different endpoints. If a lookup fails, try RDAP first (structured) and then WHOIS (legacy), and verify on the registry’s site if needed.

What to look for in RDAP/WHOIS results
  • Registrar / registry: who manages the record.
  • Status: flags like clientTransferProhibited can indicate lock/protection settings.
  • Nameservers: where DNS is delegated.
  • Dates: created / updated / expiration (often redacted for privacy).

Domain “availability” checks: what they can and can’t tell you

DNS-based checks are a strong signal, but they’re not the same as a registrar’s availability check. A domain can be registered and still have no DNS set, or be parked with non-standard records.

  • Use DNS checks for a fast first pass.
  • Confirm at a registrar before committing to branding or marketing material.
Open Domain Availability Checker

Troubleshooting tips

  • If your IP changes when a VPN is enabled, you’re seeing the VPN exit IP (expected).
  • Mobile networks may show locations far from you (carrier routing).
  • Some endpoints block requests without HTTPS (secure context).
  • If a lookup fails, try again with the bare domain (no http/https, no path), e.g. example.com.
  • WHOIS/RDAP data can be rate-limited; repeated queries may temporarily fail.
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