Private Subnet Generator

A Raycast extension that generates random private IPv4 and IPv6 prefixes. IPv4 prefixes follow RFC 1918. IPv6 prefixes are Unique Local Addresses according to RFC 4193.

Random prefixes reduce the risk of collisions. Collisions happen when networks are merged or connected over a VPN.

Commands

Generate Private IPv4 Prefix

Generates a random /24 from 10.0.0.0/8, 172.16.0.0/12 or 192.168.0.0/16. Every free /24 is equally likely. Therefore, most prefixes come from 10.0.0.0/8.

The dropdown in the search bar restricts the pool to one of the three ranges. Include All Prefixes is the default.

Generate Private IPv6 Prefix

Generates a random /48 from fd00::/8. The 40 bits after fd are the random Global ID.

Prefix Length

Both commands accept an optional length argument. Type it after the command name in Raycast's root search. Both 20 and /20 work. Without an argument, the IPv4 command generates a /24, the IPv6 command a /48.

The list shows an error instead of a prefix in these cases:

• The length is not a number.
• The length is out of range, like /33 for IPv4.
• The length is shorter than every pool, like /7 for IPv4.
• Every subnet of that length is excluded, like /17 in 192.168.0.0/16.

With Include All Prefixes, only the pools that fit the length are used. For example, /12 only draws from 10.0.0.0/8 and 172.16.0.0/12.

Actions

Action	Shortcut
Copy to Clipboard	↵
Generate New Prefix	⌘ N (macOS), ⌃ N (Windows)
Remove Entry	⌃ X
Clear History	⌃ ⇧ X

Remove Entry and Clear History are available on history entries.

History

Previously generated prefixes appear in a History section below the new prefix. The newest entry comes first. Each command keeps its own history.

The extension preferences control the history:

• History turns the history on or off. It is on by default. When it is off, the next launch of either command deletes all stored entries.
• History Size sets how many previous prefixes each command keeps. The default is 20. An empty or invalid value falls back to 20. 0 hides the history.

Excluded Ranges

A generated prefix never overlaps one of the following ranges.

IANA Special-Purpose Registries

All blocks of the IPv4 and IPv6 special-purpose address registries are excluded. The Private-Use and Unique-Local blocks are the exception, because they are the pools themselves.

Common Defaults

Vendors and tools use these ranges by default.

Range	Used by
10.0.0.0/24	Xfinity gateways
10.0.1.0/24	Apple AirPort
10.42.0.0/16	k3s pod network
10.43.0.0/16	k3s service network
10.88.0.0/16	Podman default network
10.96.0.0/12	Kubernetes (kubeadm) service network
10.244.0.0/16	Flannel pod network
10.254.0.0/16	Router loopbacks and infrastructure
10.255.0.0/16	Router loopbacks and infrastructure
172.17.0.0/16	Docker default bridge
192.168.0.0/24	Consumer routers
192.168.1.0/24	Consumer routers
192.168.2.0/24	Telekom Speedport, Belkin
192.168.100.0/24	Cable modem management (DOCSIS)
192.168.178.0/24	FRITZ!Box
fd00::/48	All-zero Global ID
fd00:ec2::/32	AWS VPC services (DNS, NTP, IMDS)
fdff:ffff:ffff::/48	All-ones Global ID

The ranges are defined in src/lib/ranges.ts.