IP Address Analyzer

Verbose subnet calculator with address classification flags.

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NetTests can run this check on a schedule, preserve historical results, compare changes over time, and alert you the moment something breaks.

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Frequently Asked Questions

How is IP Address Analyzer different from Subnet Calculator?

Subnet Calculator focuses on Classless Inter-Domain Routing (CIDR) subnet math — network address, broadcast, host range, and mask. IP Address Analyzer is more verbose: it additionally classifies the address (unicast, multicast, loopback, private, link-local, reserved, Automatic Private IP Addressing (APIPA)) and shows Internet Protocol version 4 (IPv4)-mapped Internet Protocol version 6 (IPv6) representations, making it better for understanding what a specific address is rather than subnetting.

What is an APIPA address?

Automatic Private Internet Protocol Addressing (APIPA) addresses are in the 169.254.0.0/16 range. A device assigns itself an APIPA address when it can't reach a Dynamic Host Configuration Protocol (DHCP) server — it means the device has no valid network configuration and cannot communicate beyond the local link. Seeing 169.254.x.x on an interface indicates a DHCP failure.

What does 'private' vs 'public' address classification mean?

Request for Comments (RFC) 1918 defines three private Internet Protocol (IP) ranges not routed on the public internet: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. These are used inside Local Area Networks (LANs) and Network Address Translation (NAT) environments. Everything else is public (routable). Sending a packet to a private address from the internet will be dropped at the originating router or Internet Service Provider (ISP) boundary.