Summary

  • ARIN says 2,768 legacy prefixes, representing 1.28 million /24 equivalents, came under Registration Services Agreements in Q4 2025—the largest quarterly change in the programme’s history.
  • ARIN attributes the jump primarily to large legacy allocations. By Q3 2026, 372,877 /24 equivalents remained outside agreement, 81% below Q1 2024; the registry counted 16,212 legacy CIDR blocks.

A record quarter needs more than a record-sized number. ARIN’s presentation gives the reason for the jump: large legacy allocations did most of the lifting. In Q4 2025, 2,768 prefixes covering 1.28 million /24 equivalents came under Registration Services Agreements. ARIN called it the largest single-quarter change in the programme’s history.

That explanation changes how to read the headline. Prefix count measures the number of blocks whose agreement status changed; /24 equivalents show their combined address volume. When large allocations dominate, the volume can move dramatically while the prefix count tells only part of the story. ARIN does not say how many holders account for the quarter’s 2,768 prefixes.

The later snapshot shows the remaining scale. In Q3 2026, legacy space outside agreement stood at 372,877 /24 equivalents, 81% below Q1 2024. ARIN separately counted 16,212 legacy CIDR blocks, down 6,578 from that starting point. The record quarter was a sharp step in a programme that has continued to reduce both the reported volume and block count.

ARIN dates legacy resources to allocations issued before it began operating on 22 December 1997. Holders without an agreement can maintain registry records and reverse DNS; RPKI and Internet Routing Registry access require one. The agreement boundary therefore changes service eligibility, while the registration record remains in place.

The headline now has a driver: large legacy allocations. The outstanding question is who sits behind the count. ARIN’s published figures establish the size and direction of the change; they do not give the number of holders represented by those 2,768 prefixes. That distinction matters when the next update explains whether the remaining work is concentrated in a few large portfolios or spread across many organisations.

Sources: ARIN’s ARIN 58 recap, Data Accuracy presentation, Legacy Resources, and Legacy Resource FAQs.