Legacy IPv4 Space: What It Is and Why Buyers Pay More For It

What makes a block "legacy"

Legacy address space was assigned before the Regional Internet Registries existed. Through the 1980s and early 1990s, addresses were handed out directly by IANA and its predecessors, mostly to universities, research institutions, early network operators and large corporations, under nothing resembling the policy framework that governs allocations today.

When the RIR system was established, these existing assignments did not disappear. They were recorded in the new registries, but the holders had never signed an RIR membership agreement and had never accepted the policies that came with one. That historical accident is the whole story: legacy resources sit under a different, and generally lighter, set of registry obligations than space allocated afterwards.

Legacy versus PA space

Ordinary allocated space is usually provider aggregatable (PA): allocated to a Local Internet Registry, held under a membership agreement, and subject to the full body of registry policy. It comes with ongoing obligations: annual fees, documentation requirements, and rules about how it can be transferred or reassigned.

Legacy space carries fewer of those strings. The exact position depends on the registry region and on whether the holder has since brought the resource under a contractual relationship, but broadly, legacy holders face lighter documentation requirements, fewer conditions attached to transfers, and no membership obligation simply by virtue of holding the block.

There is one more practical difference that matters commercially: legacy blocks tend to be older, larger and contiguous. A /16 assigned in 1991 is a single clean block, not something stitched together from fragments.

Why buyers pay a premium

Several factors push legacy prices above comparable PA space.

Fewer conditions on transfer. Registry policy for allocated space typically requires the recipient to demonstrate need, sign agreements, and satisfy documentation checks. Legacy transfers are often less constrained, which shortens the process and widens the pool of eligible buyers.

No membership requirement. A buyer who does not want to become an LIR, or does not want a second one, can hold legacy space without that relationship, or arrange sponsorship instead.

Cleaner history. Legacy blocks have frequently sat with a single institutional holder for decades, seeing little or no commercial use. That tends to mean no accumulated blocklist history and no reputation baggage, which matters enormously if the addresses are destined for email or any deliverability-sensitive workload.

Scarcity. No new legacy space will ever be created. The supply is fixed and shrinking as blocks are absorbed into the contractual regime, which puts a floor under prices that ordinary allocated space does not have.

What to check before buying legacy space

The lighter regulatory position cuts both ways. Weaker registry oversight historically means the paper trail can be thinner, so verification matters more, not less.

• Chain of custody. Who has actually held the block since assignment? Organisations merge, dissolve and get acquired, and a forty-year gap can hide a lot. Establish that the seller is genuinely entitled to transfer it.
• Registry status. Confirm the current registration details and whether the resource has been brought under any contractual agreement, which changes what applies to it.
• Hijack history. Dormant legacy blocks are a well-known target for address hijacking. Check whether the space has been announced by parties with no legitimate claim to it.
• Reputation. Long dormancy usually means clean, but not always. Check the block against the major blocklists before you commit, not after.
• Regional policy. Every registry treats legacy resources slightly differently, and the rules have shifted over time. What is true in one region may not hold in another.

Where RTM Networks fits

We hold and broker both PA and legacy blocks, and we sell into the RIPE, ARIN and APNIC regions. Legacy space is a meaningful share of our inventory rather than an occasional listing, so if you are specifically after it, it is worth asking what we have rather than assuming it is unavailable.

We also act as sponsoring LIR for holders who want to keep independent resources such as legacy blocks, PI assignments and AS numbers without running their own LIR. If you already hold legacy space and are wondering what your obligations actually are, that is a conversation worth having.