A Practical Guide to Acquiring IPv4 Space

I watched a colleague spend six weeks chasing an IPv4 block, only to learn the seller had open abuse listings and stale route objects. The transfer stalled, the budget window closed, and the team had to start over.

That mess is avoidable. Acquiring IPv4 space is a repeatable process when you follow the right order and keep a clear paper trail.

ARIN exhausted its general IPv4 free pool on September 24, 2015. Since then, routable space has moved through a secondary market shaped by registry policy, not a simple checkout flow.

The work breaks into ten clear steps: prove need, size the block, get pre-approved, vet the block, contract safely, and activate cleanly. Done well, you get usable space without last-minute surprises.

Key Takeaways

A smooth transfer depends on planning policy, reputation checks, and activation as one connected project.

• IPv4 supply is fixed. ARIN pre-approval speeds sourcing and shows you have a legitimate 24-month need.
• A /24 is the practical minimum. Prefixes longer than /24 are commonly filtered on the global internet, so plan around that floor.
• Prices move with the market. Recent snapshots placed averages from the mid-$20s to low $30s per address, so compare total cost against leasing before you commit.
• Verify before funds move. Use RDAP records and Spamhaus checks to confirm clean control and acceptable reputation.
• Plan ROA, IRR, LOA, and reverse DNS early. Skipping activation steps leads to routing gaps and email delivery trouble.
• Document everything. Register reassignments within seven days and run quarterly audits on blocklists, routes, and ROAs.

What You Are Actually Buying

An IPv4 transfer gives you registry control and routing rights, not deed-style ownership.

A transfer moves registration rights from one ARIN organization to another. You gain the authority to announce the numeric block through BGP and manage the records tied to that space.

Key terms matter here. A /24 is 256 addresses and the smallest block that usually propagates worldwide. An ASN, or Autonomous System Number, identifies your network. A ROA, or Route Origin Authorization, validates route origin through RPKI. An IRR route object records how the prefix should be announced. An LOA lets an upstream announce your space. RDAP is the modern replacement for legacy Whois.

Typical buyers include mail teams that need stronger sender reputation, hosting and SaaS providers, multi-cloud network teams, and companies building a more resilient edge.

Buy Vs. Lease: Decide With Numbers

The right choice depends on hold period, cash flow, and how much control your team needs.

Leasing fits temporary traffic spikes, pilot launches, and short campaigns that last less than 18 months. Buying fits stable, multi-year use, tighter control of reputation, and cases where resale value matters.

Use a simple breakeven test. Divide the purchase price per IP by the monthly lease rate. If a /24 costs $6,400 and a similar lease is $250 a month, breakeven lands near 26 months.

Pricing shifts with block size and timing. One 2026 market snapshot estimated about $25 per address, with /24s trading in the mid-four-figure to low-five-figure range. Put that math into your procurement process so the choice stays grounded in numbers, not pressure.

Right-Size the Block

Start small, because extra addresses tie up cash and add admin work long before they add value.

ARIN’s minimum transfer size is a /24. Because prefixes longer than /24 are commonly filtered, that is also the practical floor for global propagation.

Quick mapping helps with planning: /24 equals 256 IPs, /23 equals 512, and /22 equals 1,024. Larger blocks mean more ROAs, larger PTR zones, and more monitoring. Upsize only when your utilization plan clearly supports it.

Compliance Prep: ARIN Pre-Approval

Pre-approval removes friction later, because it confirms your need before you start negotiating with sellers.

ARIN offers transfer pre-approval based on a recipient’s 24-month projected IPv4 need for NRPM 8.3 and 8.4 transfers. Reviewers usually expect a growth spreadsheet, an inventory of current assignments, and supporting evidence such as customer forecasts or migration plans.

Prepare your organization documents and utilization math early. If your demand curve jumps sharply, explain why in plain language. Clear assumptions usually move faster than perfect-looking spreadsheets with no context.

Sourcing Paths

Your sourcing path affects speed, cost, and how much risk lands on your team.

You have three main options, each with tradeoffs.

• Managed marketplace or broker: Faster access, pre-vetted blocks, compliance support, and escrow. Fees are higher.
• Private party: Lower transaction costs, but more process risk and more due diligence on your side.
• ARIN waitlist: Small allocations, uncertain timing, and limited sizes. Use it as a supplement, not a primary plan.

Due Diligence Checklist

Most expensive mistakes happen before closing, so verify the block as if you expect something to be wrong.

Run every one of these checks before you sign a contract.

• Use RDAP to validate the current registrant, chain of custody, and matching organization names.
• Confirm the block is not special-use or bogon space. Bogon space means unallocated or reserved addresses that should not route on the public internet.
• Check Spamhaus listings such as ZEN, SBL, XBL, and PBL to spot reputation issues before purchase.
• Review existing ROAs, IRR objects, and any visible hijack history for routing hygiene.
• Get a seller attestation that no active reverse DNS, DNS delegations, or cloud ACLs will remain after close.
• Request a technical test window so the seller can withdraw any live announcements before handoff.

A dirty block is not always a deal breaker, but cleanup takes time. If you need the space for outbound mail or customer traffic next month, a small discount rarely offsets weeks of remediation.

Contract Safeguards and Escrow

A strong contract protects you from bad title, bad timing, and cleanup work that should stay with the seller.

Your contract should confirm a clean title and authority to transfer. It should also require removal of all outstanding LOAs, IRR objects, and ROAs by the seller at closing, and state that the block is not listed on major blocklists when funds are released.

Use escrow or a client funds account. Release money only after ARIN confirms the transfer is complete. Also spell out what happens if ARIN rejects the transfer, who pays fees, and where all approval letters, invoices, and ticket numbers will be stored for audit.

Execute the Transfer

Fast execution comes from clear ownership of each task, not from rushing the paperwork.

When your team wants one partner to coordinate pre-approval help, block verification, blacklist cleanup, escrow handling, and the final registry handoff, it helps to compare managed options before you commit, especially if internal legal and finance reviews are already compressing the timeline. If you want a guided route with those services bundled for production use, you can buy IP addresses through a specialist that handles ARIN transfer steps end to end.

A managed provider can help with pre-approval support, block verification, escrow, and reputation cleanup, with many transfers finishing in two to three weeks. Private deals can move just as fast, but only when both sides respond quickly and keep documents consistent.

The milestone sequence is straightforward: open transfer tickets with ARIN, answer information requests quickly, update RDAP records on completion, coordinate escrow release, and save every artifact for your audit trail. Internal legal and finance delays inside your company can waste more time than ARIN review.

Network Activation and DNS Readiness

Most post-close problems show up during activation, so treat this step as part of the purchase, not an afterthought.

Create ROAs that exactly match your BGP announcements. Publish IRR route objects in ARIN’s IRR. Generate an LOA for upstreams or cloud providers, because they often require one before they will announce customer prefixes.

Reverse DNS for IPv4 relies on PTR records under in-addr.arpa, with delegation managed through ARIN’s systems. Build PTRs that match forward DNS for forward-confirmed reverse DNS, which is a common trust check for mail systems. If you send email, use an IP warmup plan and verify that reputation centers look neutral or better before volume ramps up.

Publish an RFC 8805 geofeed for your prefixes and submit corrections to major geolocation providers. Then set reminders to review those corrections, because stale geolocation data can break fraud checks, support workflows, and local service rules.

Post-Transfer Governance

Good governance keeps a clean block clean, and it makes the next transfer easier.

ARIN policy requires registering IPv4 reassignments of /29 or larger within seven days through SWIP. Keep ROAs, IRR objects, and LOAs aligned whenever your routing or delegation changes.

Run quarterly audits on blocklists, route status, and ROA validity. Keep a living SOP and a simple change log so another team member can repeat the process without guessing what happened last time.

FAQ

Most follow-up questions come down to size, timing, routing control, and ongoing upkeep.

What Size Block Should a Small Team Start With?

Start with a /24, or 256 addresses. It is the smallest block ARIN will transfer and the practical minimum for global BGP propagation. Move up only when projected utilization clearly justifies the extra overhead.

How Long Do Transfers Typically Take?

Most transfers through a managed marketplace finish in two to three weeks. Private-party transfers can take longer if documents are incomplete or ARIN asks for more justification. Pre-approval is still the best way to shorten the timeline.

Do I Need My Own ASN to Use Purchased Space?

Not always. If an upstream will originate the prefix on your behalf under its ASN, you can operate without your own. Still, having your own ASN gives you better routing control, cleaner portability between providers, and an easier path to multi-homing.

What Ongoing Fees or Tasks Apply After Purchase?

You will pay ARIN an annual registration maintenance fee based on the size of your holdings. On the operations side, plan for quarterly blocklist and ROA audits, timely SWIP updates, reverse DNS upkeep, and periodic geofeed checks to keep geolocation data accurate.

Conclusion

A disciplined process saves money, time, and operational pain.

Teams that justify need, verify reputation, contract carefully, and activate with routing and DNS already planned avoid most of the setbacks that slow these deals down. Treat the workflow as a shared SOP across procurement, network, and legal, and the next transfer will be faster and cleaner than the first.