CIDR notation and subnet masks, bit by bit
See how an IPv4 CIDR prefix becomes a contiguous subnet mask, address block size, and exact network boundary.
Read guideUnderstand IPv4 boundaries
CIDR, subnet masks, host ranges, and private space
Three focused guides explain how a prefix creates a mask, how ordinary and special host boundaries differ, and exactly what RFC 1918 private space means.
Network, broadcast, and usable hosts—with /31 and /32
Understand the ordinary IPv4 host formula and why RFC 3021 /31 point-to-point links and /32 host routes need explicit rules.
Read guidePrivate IPv4 ranges: what RFC 1918 says—and does not say
Review the three RFC 1918 private blocks and avoid confusing private addressing with every special-purpose IPv4 range or with security.
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