IP Address Analyzer — Detailed Breakdown for IPv4 and IPv6
This provides a fuller analysis than a plain subnet calculation, covering both address families: classification, every notation the address can be written in, subnet splitting, and for IPv6 the expansion between compressed and full forms. It is the reference tool for the cases where a simple mask calculation is not enough.
Why run it
IPv6 is the main reason. Its compression rules mean the same address can be written several ways, and two forms that look completely different are frequently identical — which produces firewall rules that do not match, access lists that do not apply, and configuration comparisons that report a difference where none exists. Expanding both to full form settles it immediately. The subnet splitting is equally practical when carving an allocation into equal blocks without doing the arithmetic by hand.
Why automate it
The direct case is validating configuration rather than repeating lookups: comparing the addresses in your firewall rules, access lists and documentation in a normalised form catches the mismatches that textual comparison misses entirely. As dual-stack deployment becomes normal, the number of places where the same address appears in two different representations grows, and so does the chance that one of them is subtly wrong.
What it gives you
Unambiguous handling of addresses that can be written more than one way, which is where IPv6 configuration errors overwhelmingly come from. It turns "these look different" into a definite answer.