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Anycast.ID NetToolbox

The sysadmin's Swiss Army knife

Anycast.ID NetToolbox

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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Anycast.ID NetToolbox is licensed under MIT © Anycast.ID 2025

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

SPF Flatten

Resolve include:/redirect= and output a flattened SPF with lookup counts

Quick Examples

SPF Flatten Configuration

Domain Name

Anycast.ID NetToolbox is licensed under MIT, (C) Anycast.ID 2025

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