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Which IPv4 block is reserved for private internets?

The entire 10.0.0.0/8 block is private address space.

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  1. 10.0.0.0/8 ✔
  2. 8.0.0.0/8
  3. 100.0.0.0/8

Why: RFC 1918 reserves 10.0.0.0 through 10.255.255.255 for private networks. Different organizations may reuse those addresses internally because they are not globally unique.

Huh, didn't know that: RFC 1918 also reserves 172.16.0.0/12 and 192.168.0.0/16.

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A private IP keeps its address off the public guest list.
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References

Answer: 10.0.0.0/8. RFC 1918 reserves 10.0.0.0 through 10.255.255.255 for private networks. Different organizations may reuse those addresses internally because they are not globally unique.

  1. RFC 1918: Address Allocation for Private Internets www.rfc-editor.org/rfc/rfc1918.html
    10.0.0.0 - 10.255.255.255 (10/8 prefix)
    Checked 2026-10-10.

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