About the Random IP Generator
Test data for networking code needs realistic IP addresses, and hand-writing them invites subtle bias — everyone types 192.168.1.x. This generator produces random addresses constrained to a subnet or CIDR range you specify, which makes it useful for load-test fixtures, firewall rule testing, GeoIP lookups, and seeding development databases.
Constraining generation to a CIDR matters: testing a rate limiter or an allowlist with addresses that actually fall inside (and outside) the target range exercises the boundary logic, which is where the bugs live — the first and last address of a block, the /31 edge cases, the off-by-one at the broadcast address.
Frequently asked questions
Which IP ranges are safe to use in tests and documentation?
RFC 5737 reserves 192.0.2.0/24, 198.51.100.0/24, and 203.0.113.0/24 specifically for documentation and examples — they are never routed on the public internet. For private-network simulation, RFC 1918 space (10/8, 172.16/12, 192.168/16) is the standard choice.
Why exclude network and broadcast addresses?
In a classic IPv4 subnet, the first address identifies the network and the last is the broadcast address — neither is assignable to a host. Test fixtures that include them can produce false failures (or mask real bugs) in code that correctly rejects unassignable addresses. Point-to-point /31 links are the deliberate exception (RFC 3021).
Are the generated addresses uniformly distributed?
Within the specified range, yes — each assignable address is equally likely. That uniformity is what you want for load testing hash-based sharding or rate-limiter buckets, where clustered inputs would skew the distribution and hide hot-spot behavior.
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