The field guide
Less guesswork. More understanding.
Understand public IPs, CGNAT, DNS caching, IPv6 connectivity, VPN comparisons, port forwarding, and subnetting.
Why your router and this page show different IPs
Compare your device, router, and public addresses to distinguish normal NAT, double NAT, and possible CGNAT.
Read guide Connectivity · 4 minIPv6 did not respond. What should you check?
Separate an unreachable test endpoint from a missing IPv6 address, route, or working Internet connection.
Read guide DNS · 5 minWhy DNS answers differ after a change
Use record types, TTLs, and resolver comparisons to investigate a website or email DNS change.
Read guide IP addresses · 4 minWhat an IP lookup can tell you
Understand registry records, address ranges, optional routing data, reverse DNS, and why an IP location may be wrong.
Read guide Connectivity · 3 minCompare your connection before and after a VPN
Check what changed for IPv4 and IPv6 without mistaking one browser result for a complete privacy test.
Read guide Developer tools · 4 minGet your public IP in a script
Use explicit text or JSON endpoints, force an address family when needed, and handle failures and rate limits.
Read guide Home networks · 4 minTroubleshoot port forwarding without a scanner
Check the service, local firewall, forwarding rule, and upstream NAT before trying an external connection.
Read guide IP addresses · 3 minRead a subnet without guessing the address range
Work through an IPv4 /26, understand /31 and /32 exceptions, and avoid applying IPv4 host rules to IPv6.
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