Network engineering reference
Subnet calculators & network tools that just workSubnet calculator
Fast, precise CIDR math for network engineers: IPv4 & IPv6 subnets, wildcard masks, VLSM planning and printable references. Every result is a shareable permalink and computes without JavaScript.
Featured tools
Practical tools. Real-world results.Toolbox
Calculators & tools
IPv4 Subnet Calculator
Network, broadcast, host range, wildcard mask and binary breakdown for any IPv4 CIDR block.
IPv6 Subnet Calculator
Expand or compress any address, inspect prefixes and count /64 subnets instantly.
Wildcard Mask Calculator
Convert CIDR to inverse masks for Cisco ACLs — in both directions.
IP Range to CIDR
Turn an IP range into the smallest list of CIDR blocks. Batch mode included.
VLSM Calculator
Split a network into right-sized subnets from your host requirements, largest first.
Subnet Splitter
Divide any network into N equal-sized subnets — CCNA-style questions answered instantly.
CIDR Aggregator
Merge lists of blocks into minimal supernets for route summarization — exact cover, no extras.
Subnetting Practice
Seeded random drills for CCNA prep. Share a seed, race a friend, check answers instantly.
Subnet Cheat Sheet
Every prefix from /0 to /32 in one printable table. No email gate.
Password Generator
Cryptographically secure passwords and passphrases generated in your browser — never sent anywhere.
Cron Expression Builder
Write crontab lines in plain English, validate fields and preview the next run times.
Unix Timestamp Converter
Convert epoch seconds or milliseconds to dates and back, with a live ticking clock.
UUID Generator
Bulk-generate RFC 9562 version 4 UUIDs with copy-all. Runs entirely in your browser.
IT Cost Calculators
Estimate Microsoft 365, Intune, Azure VM, backup and observability run-rates before you buy.
Budget planning
Free IT cost calculators
Paid IT platforms often meter seats, devices, compute or data volume. Use transparent estimates to see the cost drivers before opening a vendor quote.
Microsoft 365
Compare Business Basic, Standard and Premium seats.
Microsoft Intune
Model Plan 1, Plan 2 and Suite licensing.
Azure VM
Turn hourly compute into a monthly run-rate.
Backup storage
Estimate retained TB from change rate and retention.
Observability
Separate log ingestion from indexed retention.
Quick answers
Popular subnet mask references
Quick answers for the masks people actually look up — each page includes host counts, ranges, binary math, examples and FAQs:
Why ITInsightHub
Built for working engineers
Shareable results
Every calculation updates the URL. Paste a permalink into tickets, runbooks or Slack instead of screenshots.
Server-side & offline-friendly
Pages are pre-rendered on Cloudflare's edge and every tool computes without client JavaScript where possible.
RFC-accurate edge cases
/31 point-to-point links per RFC 3021, /32 host routes, CGNAT and documentation ranges handled correctly.
Cheat-sheet hubs
Sysadmin cheat sheets
Filterable, printable reference sheets for Linux administration, Microsoft environments, developer tooling and databases — Azure, Intune, PowerShell, Windows, Git, Docker, SQL and Kubernetes — with facts checked against official documentation.
Linux
Essential commands, systemd, networking, disks, permissions.
Azure
Networking, CLI and subscription limits.
Intune
Enrollment, configuration profiles, compliance.
PowerShell
Syntax reference and verified admin one-liners.
Windows
Command-line and maintenance cheat sheets.
Git
Everyday commands, undo & recover, and branching workflows.
Docker
Core run/build/exec commands, Compose, and disk cleanup.
SQL
Querying, joins, and modifying data — the portable core.
Kubernetes
kubectl commands, resources & YAML, and troubleshooting.
Guides
Learn subnetting
New to IP addressing or brushing up? Start with one of these:
- How to calculate a subnet mask — step by step with a worked example
- CIDR notation explained — what
10.0.0.0/22actually means - IPv4 vs IPv6 — what changed and what still applies
- List installed software with PowerShell — the safe way