Learning Center
WhenIP Academy
A practical learning center for novice users, operators, and anyone who wants to understand what the tools on WhenIP are actually showing across different probe locations.
Start Here
These are the best first reads if you want to understand your public IP, why IPv6 disappears, how VPNs change your results, why probe locations can differ, and what ports or traceroute actually mean.
What is an IP address?Learn what a public IP is, why it changes, and what websites can actually see.IPv4 vs IPv6Understand why some networks show one address family and others show both.How VPNs workSee how VPNs change the IP websites see and why they sometimes break detection.Why results change by probe locationCompare what different WhenIP locations see and learn why routing, CDN, and policy can change the answer.Why IPv6 is not detectedCommon causes, quick checks, and what to try next when IPv6 is missing.Ports: open, closed, filteredLearn what port scan results really mean before you assume something is broken.How traceroute worksMake sense of hops, latency, and the stars or timeouts you may see.
Guides
How to use WhenIP Port CheckA step-by-step guide to using the safe WhenIP port checker and interpreting the result.How to use WhenIP DNS LookupA quick guide to checking A, AAAA, MX, TXT, and other record types on WhenIP.How to use WhenIP Reverse DNS LookupLearn how to check reverse DNS on WhenIP and how to interpret a missing PTR record.How to use WhenIP WHOISA practical guide to reading WHOIS output and knowing which fields still matter.How to use WhenIP Subnet CalculatorLearn how to enter IPv4 and IPv6 CIDR blocks and interpret the output.How to use WhenIP WebRTC CheckUse the WebRTC tool to see what ICE candidates your browser reveals and compare results across privacy states.How to use WhenIP Header CheckUse Header Check to see what metadata the site receives with your current request path.How to use WhenIP TracerouteUse the server-side traceroute to understand the path from the WhenIP probe toward your current public IP.
Troubleshooting
IPv6 not detected: common causes and fixesSee the most common reasons IPv6 is missing and what to check on your router, VPN, and ISP path.Port open vs closed vs filtered: what do the results mean?Learn how to interpret port check results without jumping to the wrong conclusion.Why ping fails even when the internet worksSee the most common reasons ping fails and why an ICMP timeout is not the same as a service outage.Why traceroute shows stars or timeoutsLearn why traceroute often shows stars in the middle of a healthy path.Why reverse DNS is missing on some IP addressesLearn why a PTR record may be missing and why that is common for many public addresses.
Probe Locations
Some results change when you switch from San Francisco to Amsterdam, New York, or future probes. That is expected when routing, CDN behavior, filtering, or DNS policy varies by region.
Why results change when you switch probe locationsLearn why ping, traceroute, port checks, DNS answers, and even visible IP families can differ by vantage point.How traceroute worksMake sense of path changes, hops, and latency when comparing regions.What is ping?See why latency and loss can vary depending on which probe sends the test.
Reference
Common port numbers and what they are used forA practical guide to common ports and the services normally associated with them.Common DNS record types explainedA practical reference for the DNS record types most people actually troubleshoot.Private IP ranges you should recognizeA quick reference to the most important private IPv4 ranges and how they are used.Reserved IP ranges worth knowingA handy reference for special-use IP ranges that show up in troubleshooting.
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