Limits RegistryPUBLIC RECORD
Limits RegistryIPv4, standardized in RFC 791 (1981), uses a 32-bit address field, yielding a fixed maximum of 2^32 (about 4.29 billion) unique addresses. This hard ceiling, small relative to the number of internet-connected devices today, is the reason for IPv4 address exhaustion and the decades-long, still-incomplete industry migration to IPv6.
The question, scope, and sources behind this Registry record.
IPv4, standardized in RFC 791 (1981), uses a 32-bit address field, yielding a fixed maximum of 2^32 (about 4.29 billion) unique addresses. This hard ceiling, small relative to the number of internet-connected devices today, is the reason for IPv4 address exhaustion and the decades-long, still-incomplete industry migration to IPv6.
The total number of distinct 32-bit addresses definable by the Internet Protocol version 4 addressing scheme, fixed by its address field width.
Change a parameter to stress-test whether a proposed result is still inside the published specification. This is an audit aid, not a proof checker.
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Current frontiers derived from accepted Claims.
An observed or demonstrated result; no opposing bound is implied.
The frontier is not sacred
Most progress starts with a disagreement that survives contact with evidence. If you can push the known lower bound up or pull the upper bound down, show us the work.
≥ when you have shown that at least this value is achievable.≤ when you have shown that anything above this value is impossible.No vibes. State the value, define the scope, and link the paper, proof, code, or reproduction that lets another person check it. Editors review every challenge before the public record changes.
Challenge this recordAssertions tied to evidence, attribution, and review.
The frontier as it changed over time.
Only accepted Claims matching the current specification contribute to the displayed bounds. Strict inequalities remain open; contradictory Claims require editorial review.
Permanent ID limitsregistry.com/limits/LR-IPV4-ADDRESS-SPACE
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Limits Registry. LR-IPV4-ADDRESS-SPACE. IPv4 total address space size. 2026.