Free networking tools
10 tools, no sign-up, no limits. And because each one shares its math with the NetForge-AI simulator, you can take any answer straight into the lab and prove it with a ping.
Subnet Calculator
Network and broadcast address, usable host range, subnet + wildcard mask, address class and type — for any IPv4 CIDR.
Open toolCIDR / Netmask Converter
Convert between CIDR prefix length, subnet mask, and wildcard mask instantly — plus a quick-reference table of every common prefix.
Open toolVLSM Planner
Give it one block and your per-subnet host counts; get a largest-first VLSM allocation with every subnet's full breakdown.
Open toolWildcard Mask Converter
Convert between prefix length, subnet mask, and ACL wildcard mask — with a ready-to-paste access-list example.
Open toolInteractive OSI Model
Click through all 7 layers of the OSI model — protocols, PDU names, devices, and real-world analogies for each layer.
Open toolMAC Address Lookup
Vendor (OUI) lookup in any notation, plus what the I/G and U/L flag bits say about how the frame will be delivered.
Open toolIP to Binary Converter
IPv4 in dotted decimal, binary, hex, and 32-bit integer — with the per-octet breakdown that makes subnetting click.
Open toolPort Number Lookup
Searchable TCP/UDP port reference with the security and configuration caveat that matters when you write the rule.
Open toolMTU & MSS Calculator
Stack GRE, IPsec, VXLAN, PPPoE, and WireGuard overhead to get the effective MTU, the right MSS, and the config lines.
Open toolDNS Record Types
Every record type that matters, with a real zone-file example and the specific mistake that makes each one fail.
Open toolWant the theory behind the math? IPv4 Subnetting in 20 minutes is free, hands-on, and opens in the lab.