SubnetDeck: Subnet Calculator

SubnetDeck is an offline subnet calculator and IP address planning kit for network engineers and IT staff. It never connects to the internet, so it keeps working in server rooms, data centers, factories, closed networks and during outages. FREE • IPv4 and IPv6 calculator with a keypad that only accepts valid input (hardware keyboards supported) • Binary boundary bar that shows exactly where the network bits end • Network, broadcast, first and last address, usable hosts, wildcard mask and reverse DNS zone • /31 (RFC 3021) and /32 handled correctly; special-purpose addresses identified • 11 Learn topics: masks and prefixes, why two addresses are subtracted, five kinds of overlap, VLSM and FLSM, IPv6 and more • 13 of the 69 playbooks PREMIUM (one-time In-App Purchase, no subscription) • All 69 playbooks in 9 categories: private ranges, single sites, multi-site WAN with route aggregation, point-to-point links, segmentation, cloud networks, hybrid and migration, factory IT/OT separation, and IPv6 • Each playbook explains the reasoning, room to grow and pitfalls, and turns into a design plan with one tap • Design tab: segments by host count or prefix length, automatic VLSM allocation, overlap and issue detection • Folders for each site, customer or company, so every network's addressing stays on your device • Search plans by address: which plan contains 10.1.2.3, and which overlaps a block • Tools: equal split (FLSM), route summarization and overlap check • Export to Markdown, CSV and .xlsx; export and import all plans when you change devices • Reserved-address deduction profiles for cloud subnets • Optional inclusion of your plans in iCloud Backup PRIVATE BY DESIGN • No network connections, no ads, no analytics, no account • Plans are stored only on your device with file protection and are excluded from backups unless you choose otherwise • The app switcher preview hides your plans For iPhone, iPad, Mac and Apple Vision Pro. Fully localized in 9 languages: English, Japanese, Spanish, German, French, Portuguese (Brazil), Chinese (Simplified and Traditional) and Korean.