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Networking Toolbox

The sysadmin's Swiss Army knife

Subnetting
CIDR
IP Tools
DNS Tools
DHCP
Lookups
Ref

Networking Toolbox

Subnetting

  • IPv4 Subnet Calculator
  • IPv6 Subnet Calculator
  • VLSM Calculator
  • Supernet Calculator
  • Subnet Planner

CIDR Tools

CIDR Masks

  • CIDR → Mask
  • Mask → CIDR

Set Operations

  • Difference (A - B)
  • Overlap (A ∩ B)
  • Contains (A ⊆ B)

More

  • IP Range to CIDR
  • CIDR Summarizer
  • CIDR Split
  • Next Available Subnet
  • Free Space Finder
  • CIDR Deaggregate
  • CIDR Compare
  • CIDR Allocator
  • CIDR Alignment
  • Wildcard Mask Converter

IP Tools

Number Formats

  • Format Representations

Address Calculations

  • IP Distance Calculator
  • Nth IP Calculator
  • Random IP Generator
  • IP Regex Generator
  • IP Address Validator
  • IP Enumerate

IPv6 Notation

  • IPv6 Expand
  • IPv6 Compress
  • IPv6 Normalizer
  • IPv6 Zone ID Handler
  • IPv6 Solicited-Node
  • IPv6 Teredo Parser
  • IPv6 NAT64 Translator

IP Families

  • IPv4 → IPv6
  • IPv6 → IPv4

Address Generation

  • EUI-64 Converter
  • ULA Generator
  • MAC Address Converter

dhcp

DHCPv4 Options

  • Option 3 - Default Gateway
  • Options 6/15 - DNS & Domain
  • Option 51 - Lease Time
  • Option 43 - Vendor Specific
  • Option 60 - Vendor Class
  • Option 61 - Client ID
  • Option 82 - Relay Agent
  • Option 119 - Domain Search
  • Option 121/249 - Classless Routes
  • Options 150/66/67 - TFTP Server
  • PXE Boot Profile
  • Freeform TLV Composer

DHCPv6 Options

  • Options 23/24 - DNS Servers & Search
  • Options 25/26 - Prefix Delegation
  • Option 39 - Client FQDN

DHCPv6 Identity

  • DUID Generator
  • IAID Calculator

Calculators & Planning

  • Lease Time Calculator
  • Fingerprinting Database

Configuration Generators

  • Kea/ISC Config Snippets

DNS

DNS Generators

  • PTR Generator

Reverse DNS

  • PTR Generator
  • Reverse Zone Generator
  • Reverse Zones Calculator
  • PTR Sweep Planner

Record Generators

  • A/AAAA Bulk Generator
  • CNAME Builder
  • MX Record Planner
  • SRV Record Builder
  • TXT Record Escape Tool
  • SPF Policy Builder
  • DKIM Key Generator
  • DMARC Policy Builder
  • CAA Record Builder
  • TLSA Generator
  • SSHFP Generator
  • SVCB/HTTPS Builder
  • NAPTR Builder
  • LOC Builder
  • RP Builder
  • IDN Punycode Converter

DNS Utilities

  • DNS Record Validator
  • TTL Calculator
  • EDNS Size Estimator
  • DNS Label Normalizer

Zone File Tools

  • Zone Linter
  • Zone Diff
  • Zone Statistics
  • Name Length Checker

DNSSEC Tools

  • DNSKEY Key Tag Calculator
  • DS Record Generator
  • NSEC3 Hash Calculator
  • CDS/CDNSKEY Builder
  • RRSIG Planner

Diagnostics

DNS Diagnostics

  • DNS Lookup
  • Reverse DNS Lookup
  • DNS Propagation Checker
  • SPF Record Evaluator
  • DMARC Policy Checker
  • CAA Effective Policy
  • NS/SOA Consistency Check
  • DNSSEC AD Flag Checker
  • DNSSEC Validation Chain
  • DNS Blacklist Checker
  • AXFR Security Tester
  • DNS Query Performance
  • SOA Serial Analyzer
  • DNS Trace
  • Glue Check
  • SPF Flatten

HTTP Diagnostics

  • HTTP Headers Analyzer
  • Redirect Trace
  • Security Headers Analyzer
  • CORS Policy Checker
  • HTTP Performance Analyzer
  • HTTP Compression Check
  • Cookie Security Inspector

TLS Diagnostics

  • TLS Certificate Analyzer
  • TLS Versions Probe
  • TLS ALPN Negotiation
  • OCSP Stapling
  • Cipher Presets
  • Service Banner Grabber
  • TLS Handshake Analyzer
  • CT Log Search

Network Diagnostics

  • TCP Port Checker
  • HTTP Ping
  • BGP Route Lookup
  • IPv6 Connectivity Checker
  • ASN & Geolocation Lookup

Email Diagnostics

  • MX Health Checker
  • SPF Policy Checker
  • DMARC Policy Checker
  • SMTP TLS Checker
  • Greylisting Tester

RDAP Diagnostics

  • Domain RDAP Lookup
  • IP Address RDAP Lookup
  • ASN RDAP Lookup

Reference

Fundamentals

  • CIDR Notation Explained
  • VLSM in Plain English
  • Route Summarization / Supernetting

IPv6 Addressing

  • IPv6 Address Types & Key Prefixes
  • Common IPv6 Prefix Lengths
  • IPv4 in IPv6
  • IPv6 Privacy Addresses

Special Addresses

  • Common Subnet Sizes
  • Network Classes (A/B/C)
  • Reserved IP Ranges
  • Special-Use IPv4 Blocks (RFC 6890)
  • Private vs Public IP Addresses
  • Carrier-Grade NAT Explained
  • Link-Local & APIPA Addresses
  • IPv4 & IPv6 Multicast Basics

DNS & Protocols

  • Reverse DNS (PTR Records)
  • Reverse Zones for CIDR Delegation
  • ICMP & ICMPv6: Common Types
  • ARP vs NDP

Network Operations

  • What is an ASN?
  • Common TCP/UDP Ports
  • ACL Wildcard Masks
  • Common MTU/MSS Values
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Networking Toolbox is licensed under MIT © Alicia Sykes 2025

Accessibility Policy

Making networking tools accessible to everyone.

Our Commitment

Networking Toolbox is designed to be accessible to everyone. We meet WCAG 2.1 Level AA standards and continuously work to improve accessibility for all users.

Accessibility Features

  • Fully keyboard navigable - use Tab, Enter, and arrow keys to navigate without a mouse
  • Screen reader compatible - tested with NVDA, JAWS, and VoiceOver
  • Customizable display options in Settings:
  • • High contrast themes
  • • Adjustable text size
  • • Dyslexic-friendly font option
  • • Enhanced focus indicators
  • • Reduced motion mode
  • Semantic HTML and ARIA labels throughout
  • Clear color contrast ratios
  • Alternative text for all images and icons

Feedback & Improvements

We welcome feedback on accessibility issues. If you encounter any barriers while using Networking Toolbox, please open an issue on GitHub or contact us directly. Pull requests for accessibility enhancements are always appreciated.

Report an accessibility issue

Third-Party Content

While we strive to ensure our platform is accessible, some diagnostic tools may interact with third-party services beyond our control. We do our best to present this information accessibly.

Networking Toolbox is licensed under MIT, (C) Alicia Sykes 2025

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