Random IP Generator

What this tool is used for

• Producing addresses to populate a test fixture or a seed database.
• Generating input to exercise an address parser or a validator.
• Filling a mock log file with plausible-looking addresses.
• Producing sample data for a dashboard screenshot without using real addresses.
• Testing how a UI renders long IPv6 addresses.

Frequently Asked Questions

Are these safe to use in tests?

Only if you avoid live space. Public IPv4 addresses belong to real hosts, so a randomly generated one may point at somebody's server. For safety use the RFC 5737 documentation ranges 192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24, which are reserved and never routed.

Which ranges are private?

RFC 1918 defines 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Also reserved: 127.0.0.0/8 loopback, 169.254.0.0/16 link-local, 224.0.0.0/4 multicast, and 100.64.0.0/10 carrier-grade NAT.

How do random IPv6 addresses differ?

The space is vastly larger — 128 bits versus 32 — so collisions are irrelevant, but formatting matters: RFC 5952 requires lowercase hex and a single :: compressing the longest run of zeros. Documentation space is 2001:db8::/32.

Can I generate addresses within a specific subnet?

Yes — give a CIDR block and addresses are drawn from its host range. Remember the network address and, on IPv4, the broadcast address are not assignable, so a /24 offers 254 usable hosts rather than 256.

Will these pass validation?

They are syntactically valid and will satisfy format checks and regex rules. They will not resolve or respond to traffic, which is usually the point — they exercise parsing and storage without touching the network.

What is the difference between CIDR notation and a plain range?

CIDR expresses a block as a prefix length — /24 fixes the first 24 bits, giving 256 addresses. An arbitrary start-and-end range often cannot be written as a single CIDR block at all, which is why one firewall range sometimes needs several rules.

Which addresses should never appear in generated data?

Loopback 127.0.0.0/8, link-local 169.254.0.0/16, multicast 224.0.0.0/4 and the reserved 240.0.0.0/4. They look valid and behave specially, so a fixture containing one produces behaviour that has nothing to do with what the test intended to check.

Which documentation ranges are reserved for examples?

192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24, defined by RFC 5737 precisely so examples cannot collide with a real host. They are the correct choice for anything published.

Common errors and gotchas

• Using generated addresses in a test that actually connects, since they may belong to someone real.
• Assuming every generated address is routable, when many fall in reserved or private ranges.
• Treating random addresses as a substitute for realistic distribution, which real traffic is not.
• Overlooking that a random IPv6 address is almost certainly unallocated and behaves differently.
• Putting generated addresses in an allowlist or a firewall rule by mistake.