PrefixForge: IPv4 Subnet Tools

Plan IPv4 networks with clear CIDR arithmetic and saved local notes. PrefixForge is an offline tool for developers, network learners and anyone organizing an address plan.

• Enter an IPv4 host or network with a /0–/32 prefix. See the normalized network, subnet mask, directed broadcast, wildcard mask, address range and host capacity. • Understand /31 point-to-point endpoints and /32 host routes with explicit explanations instead of misleading network/broadcast reservations. • Split a parent network into equal-size child subnets, with up to 256 rows. Inspect each child’s boundaries or share the subnet table as text. • View binary addresses and masks, plus the count of network and host bits. • Check whether an address lies inside a CIDR block. • Classify the input address against common private, shared, link-local, loopback, documentation and other special ranges. • Save named network plans with purpose and reservation notes. Edit, delete and export them as text. • Consult an offline table of all 33 prefix lengths and original explanations of CIDR planning.

Works on iPhone and iPad with no account, ads, analytics, tracking or in-app purchases. Calculations and saved plans work entirely offline.

PrefixForge calculates address boundaries; it does not discover devices, scan networks, test connectivity, configure equipment, or check address availability. Host counts describe conventional arithmetic capacity and may not equal assignable capacity in special-purpose ranges. The common-range table is not exhaustive and is not a live allocation or routability database. IPv6, VLSM optimization and DNS lookup are not included.

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