Small tools for real network questions.
Each tool does one job, explains the result, and tells you what to check next. No account, dashboard, or diagnostic software required.
Public IP checker
See the IPv4 or IPv6 address visible to websites, plus the associated network, ISP, hostname, and approximate location.
Instant resultOpen tool → ReachabilityOpen port checker
Test whether selected TCP ports on a public address or hostname accept an inbound connection from the internet.
Permission requiredOpen tool → AddressingIPv4 subnet calculator
Calculate the network address, subnet mask, broadcast address, host range, wildcard mask, and address count.
Runs in your browserOpen tool →A result is only useful in context.
These tools observe one part of a connection. Pair the output with the correct next step.
That is normal on a dynamic ISP connection. Recheck after reconnecting your modem or VPN.
Check the service, host firewall, router forwarding, carrier-grade NAT, and whether your ISP filters it.
Start with the CIDR prefix. It determines which bits identify the network and which identify a host.