Reserved IP ranges worth knowing
Not every IP block is meant for the public internet. Special-use ranges exist for loopback, link-local, documentation, multicast, testing, and more.
- Which ranges are special-purpose.
- Why they appear in logs and local diagnostics.
- How to avoid misreading them.
Important IPv4 examples
127.0.0.0/8 is loopback.
169.254.0.0/16 is link-local.
100.64.0.0/10 is carrier-grade NAT shared space.
192.0.2.0/24, 198.51.100.0/24, and 203.0.113.0/24 are documentation blocks.
Important IPv6 examples
::1/128 is loopback.
fe80::/10 is link-local.
fc00::/7 covers unique local addresses.
2001:db8::/32 is documentation space.
Why it matters
Spotting a reserved range quickly helps you understand whether the address is local, lab-only, documentation-only, or truly public.
What to do with the info
Use reserved ranges in examples and docs.
Avoid assuming a strange-looking address is public until you classify it.
Why do tutorials use 203.0.113.x?
Because it is reserved for documentation.
Can link-local addresses reach the internet?
No. They are for the local segment only.
Last updated: March 29, 2026