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203.0.113.0/24

203.0.113.0/24 (TEST-NET-3) is reserved for documentation and examples.

Last updated 2 Nov 2026 from the IANA IPv4 Special-Purpose Address Registry

Short answer

203.0.113.0/24 (TEST-NET-3) is reserved for documentation and examples.

Block203.0.113.0/24
First – last203.0.113.0 – 203.0.113.255
Size256 addresses
Name in the registryDocumentation (TEST-NET-3)
Defined inRFC 5737
Allocated2010-01
Valid as source / destinationFalse / False
ForwardableFalse
Globally reachableFalse

What it means

RFC 5737 reserves it, alongside 192.0.2.0/24 and 198.51.100.0/24, so that manuals and examples never point at a real network.

No device on the internet should use it.

Want the address websites actually see for you? Open the Truth Check.

Sources

  1. IANA IPv4 Special-Purpose Address Registry (CC0) · checked 2 Nov 2026
  2. RFC 5737