Classless Inter-Domain Routing (CIDR) Tools

Free online Classless Inter-Domain Routing tools and open API


Free online tools focused on reliability and speed.
For developers, we offer free public REST APIs: IP to geolocation, hostname information, user-agent string parser, identicon generator and more

CIDR information and calculator

Analyze a CIDR

Example: or 2001:db8::/32

You said REST API ?

Each online tool has an associated REST API

Find the tool you need and the page will also provide the associated public and free REST API documentation. If you can't find what you're looking for, feel free to contact us and we'll be happy to help you sort it out.

Special-Purpose Address Registry

The below table contains all the special-purpose IANA registered address blocks.

IP Version 4

Address Block Name This host on this network Private-Use Shared Address Space Loopback Link Local Private-Use IETF Protocol Assignments IPv4 Service Continuity Prefix Traversal Using Relays around NAT Anycast NAT64/DNS64 Discovery NAT64/DNS64 Discovery IPv4 dummy address Port Control Protocol Anycast Documentation (TEST-NET-1) Private-Use Direct Delegation AS112 Service AS112-v4 AMT Deprecated (6to4 Relay Anycast) Benchmarking Documentation (TEST-NET-2) Documentation (TEST-NET-3) Reserved Limited Broadcast

IP Version 6

Address Block Name
100::/64 Discard-Only Address Block
2001:10::/28 Deprecated (previously ORCHID)
2001:1::1/128 Port Control Protocol Anycast
2001:1::2/128 Traversal Using Relays around NAT Anycast
2001:20::/28 ORCHIDv2
2001:2::/48 Benchmarking
2001:3::/32 AMT
2001:4:112::/48 AS112-v6
2001:5::/32 EID Space for LISP (Managed by RIPE NCC)
2001::/32 TEREDO
2001:db8::/32 Documentation
2002::/16 6to4
2620:4f:8000::/48 Direct Delegation AS112 Service
64:ff9b:1::/48 IPv4-IPv6 Translated Address
64:ff9b::/96 IPv4-IPv6 Translated Address
:: Loopback Address
::/128 Unspecified Address
::ffff:0:0/96 IPv4-mapped Address
fc00::/7 Unique-Local
fe80::/10 Link-Local Unicast