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Which of these address blocks is reserved for private networks by RFC 1918?

172.16.0.0 to 172.31.255.255 (172.16.0.0/12) is private, along with 10.0.0.0/8 and 192.168.0.0/16.

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  1. 172.0.0.0 to 172.15.255.255
  2. 169.254.0.0 to 169.254.255.255
  3. 172.16.0.0 to 172.31.255.255 ✔

Why: RFC 1918 reserves three private blocks: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Anyone can reuse them inside their own network without asking a registry. The other two ranges are not RFC 1918 blocks.

Huh, didn't know that: Private addresses are only unique inside one enterprise, which is why routers need NAT to reach the internet.

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My network is so private that even its own packets have to show ID at the 192.168 door.
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References

Answer: 172.16.0.0 to 172.31.255.255. RFC 1918 reserves three private blocks: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Anyone can reuse them inside their own network without asking a registry. The other two ranges are not RFC 1918 blocks.

  1. IETF RFC 1918, Address Allocation for Private Internets www.rfc-editor.org/rfc/rfc1918
    172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
    Checked 2026-10-10.

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