Free network engineering tools

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Professional subnet calculators, Cisco IOS script generators, and topology simulators. No login required. Runs entirely in your browser.

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Subnet Calculator Free

IPv4 CIDR subnet calculator

Enter any CIDR block and instantly get network address, broadcast, usable host range, wildcard mask, and binary representation.

$ subnet 192.168.1.0/24

Network 192.168.1.0

Broadcast 192.168.1.255

Hosts 192.168.1.1 — .254 (254 usable)

Open calculator →
Cisco Scripts Free

IOS Script Generator

Generate interface configs, OSPF, static routes, and extended ACLs ready to paste into the console.

Generate script →
Topology Beta

Topology Simulator

Drag-and-drop network topology builder with automatic IP assignment and adjacency tables.

Build topology →

Also available

VLSM Planner + Networking articles

Variable Length Subnet Masking allocator and curated networking guides, subnet cheat sheets, and OSPF configuration examples.

VLSM Planner → Read articles →