Networking Signal Toolbox
Eleven free tools for network engineers
Subnetting, mask conversion, IPv6 prefix planning, VLAN design, PoE budgeting, bandwidth sizing, binary conversion, router lookups and exam practice. Everything runs in your browser, with nothing to install, no account and no limits.
Subnetting & Addressing
5 tools
Subnet Calculator
Enter any IPv4 address and CIDR prefix to get the network and broadcast addresses, usable host range, wildcard mask and binary mask. Handles /31 and /32 correctly.
CIDR to Subnet Mask Converter
Convert a prefix to a mask and back, in both directions, with the wildcard mask, address counts and binary. Rejects non-contiguous masks and includes the full /0 to /32 table.
IPv6 Subnet Calculator
Split any IPv6 prefix into smaller networks. Shows how many subnets you get, the addresses in each, and the first prefixes written out in RFC 5952 form. Warns when a prefix longer than /64 will break SLAAC.
VLAN Calculator
Plan a multi-VLAN network. Add departments, pick a subnet size, and get an aligned IP plan with gateways plus a ready-to-paste Cisco IOS configuration.
IP to Binary Converter
Convert any IPv4 address to binary, hexadecimal and its 32-bit decimal value, with a per-octet breakdown. Includes the manual method for exam conditions.
Capacity & Power
3 tools
PoE Power Budget Calculator
Add access points, cameras and phones against your switch’s PoE budget. Toggles between real device draw and the worst case figure a switch reserves when it allocates by class.
Bandwidth Calculator
Work out how much bandwidth an office or home actually needs, based on user count, concurrency and the applications in use, with sensible headroom built in.
WiFi Speed Test & Analyser
Run a speed test, then find out what your Mbps figure means for streaming, gaming, calls, and how many people your connection genuinely supports.
Reference & Lookup
2 tools
Default Router IP Finder
Default gateway, username and password for 40+ router brands, plus how to find your own router’s IP on Windows, macOS, Linux, Android and iPhone.
Certification Comparison
CCNA, CCNP, CCIE, Network+, Security+, AWS and Azure compared on cost, exam code, difficulty, validity and salary range. Filter by level or vendor.
Practice & Exam Prep
1 tool
OSI Model Quiz
20 questions on the seven layers, with an explanation after every answer. Instant scoring, unlimited retakes, and built for CCNA, Network+ and interview prep.
Which Tool Should You Use?
| If you need to… | Use |
|---|---|
| Split a network into smaller subnets | Subnet Calculator |
| Turn a /26 into 255.255.255.192, or the reverse | CIDR to Subnet Mask Converter |
| Divide an IPv6 prefix into /64 segments | IPv6 Subnet Calculator |
| Design VLANs for departments and generate switch config | VLAN Calculator |
| Understand how a subnet mask works bit by bit | IP to Binary Converter |
| Check a switch can power your cameras and access points | PoE Power Budget Calculator |
| Decide what internet plan to buy | Bandwidth Calculator |
| Work out whether your current speed is enough | WiFi Speed Test |
| Log in to a router you do not have the details for | Default Router IP Finder |
| Choose which certification to study next | Certification Comparison |
| Test what you actually remember | OSI Model Quiz |
Why These Tools Exist
Most online subnet calculators give you a number and nothing else. These are built the other way round, so every tool shows its working, explains what each field means, and links to the guide that covers the theory behind it. The VLAN calculator outputs real Cisco IOS you can paste into a switch. The subnet calculator handles the /31 point-to-point exception that trips up most tools. The CIDR converter rejects masks like 255.0.255.0 that most tools quietly accept. The IPv6 calculator tells you when a prefix longer than /64 will stop address autoconfiguration working, which is the mistake that makes an otherwise correct plan fail. The PoE calculator shows the worst case class allocation figure, which is the number that actually exhausts a switch budget rather than the device draw everyone adds up. The bandwidth calculator refuses to let you size a circuit for 100% concurrency, because that is how people end up paying for three times what they need.
They run entirely in your browser. Nothing you type is sent anywhere, which matters when you are pasting internal addressing into a form.
Learn the Theory Behind the Tools
Every tool has a matching guide. Start with networking fundamentals, then work through routing protocols, switching and VLANs, and network security. For configuration practice, our BGP configuration guide walks through a full eBGP and iBGP lab with real command output.
Preparing for an interview? Our top 50 networking interview questions covers what actually gets asked, and the OSI model complete guide is the reference behind the quiz.