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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

Fundamentals
CIDR Notation ExplainedVLSM in Plain EnglishRoute Summarization / Supernetting
IPv6 Addressing
IPv6 Address Types & Key PrefixesCommon IPv6 Prefix LengthsIPv4 in IPv6IPv6 Privacy Addresses
Special Addresses
Common Subnet SizesNetwork Classes (A/B/C)Reserved IP RangesSpecial-Use IPv4 Blocks (RFC 6890)Private vs Public IP AddressesCarrier-Grade NAT ExplainedLink-Local & APIPA AddressesIPv4 & IPv6 Multicast Basics
DNS & Protocols
Reverse DNS (PTR Records)Reverse Zones for CIDR DelegationICMP & ICMPv6: Common TypesARP vs NDP
Network Operations
What is an ASN?Common TCP/UDP PortsACL Wildcard MasksCommon MTU/MSS Values
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IPv4 in IPv6
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Common Subnet Sizes
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Networking Toolbox is licensed under MIT, (C) Alicia Sykes 2025

About • GitHub • Sponsor • More Apps →