How ISPs Evaluate IPv4 Supply Sources: A Practical Guide

Where an ISP gets its IPv4 addresses has quietly become one of the biggest procurement calls in the business. The free pools are gone. Operators now have to pick between waiting lists at the regional registries, brokers, or leasing — and each path comes with very different costs, risks, and trade-offs in flexibility. This guide lays out how ISPs actually evaluate these options, with real numbers for price, risk, and how much control you keep.

The IPv4 Shortage: Why Supply Strategy Matters for ISPs

Back in 2011, IANA handed out the last /8 blocks to the RIRs. Since then, every regional registry has run dry, and the market price of a single IPv4 address has climbed from under $5 to somewhere in the $30–$60 range, depending on block size and region. For an ISP standing up a new consumer network, a /22 — just 1,024 addresses — can run into five figures. Carriers who need a /16? Budgets in the millions.

And the shortage bites in more places than the purchase price alone:

• CGNAT trade-offs: Plenty of ISPs stretch their scarce addresses with carrier-grade NAT. It works, sort of. But shared addresses degrade gaming, VoIP, and peer-to-peer performance, and that shows up later as churn and heavier support loads.
• Growth constraints: Providers entering a new market often can’t get public space fast enough through the usual channels. Launches get delayed. Sometimes by a lot.
• Compliance exposure: Addresses picked up informally may carry a hijacking history, RPKI gaps, or disputed ownership — routing headaches and legal risk bundled together.

A disciplined supply strategy weighs price against transfer speed and long-term control. Marketplaces like IP4 Market, which verify inventory and support clean transfers, sit somewhere in the middle: faster than the registry channels, safer than private deals.

RIR Pools: Waiting Lists, Costs, and Limitations

Each of the five regional registries handles exhausted supply a little differently. Worth understanding the mechanics before you commit to this route:

1. Waiting lists: ARIN and RIPE NCC keep lists for returned or reclaimed prefixes. Waits of 12–36 months are common, and there’s no telling what block size you’ll get. APNIC and LACNIC run similarly constrained queues.
2. Direct allocation fees: Setup costs aside, annual maintenance fees apply for as long as you hold the allocation — ARIN’s resource fees, for instance, scale with block size.
3. Eligibility requirements: LIRs under RIPE policy can request allocations, but end-user assignments require demonstrated need, documentation, and sometimes justification reviews that add weeks to the timeline.

Here’s the blunt version: the registry channel is essentially closed to new demand. Waiting lists recover a few million addresses a year globally, against demand measured in the tens of millions. You do the math. Keep your organization on the relevant waiting list anyway — it’s cheap to stay in the queue — but never build a launch plan around it. Treat registry space as a supplement. Budget for the market as your primary path.

Leasing IPv4 Space: Flexibility vs. Long-Term Control

Leasing has become the go-to short-term model. Typical rates run $0.10 to $0.30 per address per month, depending on block size and contract length. A /23 at $0.20 per address costs roughly $4,900 a year. Buying that same space outright? $40,000–$60,000.

Leasing makes sense for ISPs in a few specific situations:

• Uncertain demand: Testing a new market, or scaling seasonally, without locking up capital.
• Bridge strategy: Covering CGNAT overflow while you raise the money for a purchase.
• Block-size flexibility: Getting access to prefixes smaller or larger than what’s actually for sale.

The trade-off is control. Lessors can terminate contracts, raise rates at renewal — or run into their own insolvency, leaving you to renumber in a hurry. Any numbering plan built on leased space should include an exit plan: NAT headroom, documented renumbering runbooks, and contractual notice periods of at least six months.

Vetting the counterparty matters as much as the economics. Verified marketplaces like IP4 Market check lessor legitimacy, prefix history, and RPKI readiness before listing any inventory — a step worth not skipping.

Buying Through IPv4 Marketplaces: What to Look For

Marketplaces remain the most efficient channel for outright purchases. That said, not all platforms are equal — not even close. Before committing to any listing, run it through these criteria:

• Ownership verification: The platform should confirm the seller’s legal right to transfer the block. Ideally that means reviewing regional internet registry (RIR) records and corporate documentation, not just taking someone’s word for it.
• Reputation screening: Clean blocks matter. A /22 with residual spamhaus listings or a hijack history can cost you weeks of remediation. Weeks you don’t have. Demand evidence of blacklist checks and routing history.
• Escrow and transfer management: Reputable marketplaces handle funds through escrow and coordinate RIR transfers directly, which cuts counterparty risk substantially.
• Pricing transparency: Look for published per-address pricing and historical transaction data. Opaque “request a quote” models? Walk away.

IP4 Market, for example, verifies sellers, screens block reputation, and supports the full transfer workflow — one reason many ISPs treat it as their default procurement channel. When comparing platforms, ask for references from other ISP operators who have completed transfers of similar size. A quick call saves a lot of grief later.

Comparing IPv4 Supply Sources: Cost, Risk, and Reputation Checklist

Here’s a consolidated framework. Use it before committing to any acquisition path:

1. Cost per address over three years: Factor in acquisition price, transfer fees, RIR charges and — for leases — annual rental escalation. A $55/address purchase often beats a $1.50/address annual lease within four years.
2. Counterparty risk: Brokers with unverifiable ownership claims and private lease deals without contracts carry the highest risk. Verified marketplaces and direct RIR transactions carry the lowest. Simple as that.
3. Block reputation: Check every candidate block yourself against major blacklists, BGP hijack databases and historical routing announcements. Independently. Before signing anything.
4. Regulatory compliance: Confirm the transfer follows RIR transfer policies, including RPKI ROA creation and correct organizational documentation.
5. Operational fit: For most ISP routing plans, a /22 of contiguous space beats four /24s scattered across different announcements. It just does.

Scoring each source against these five dimensions turns an emotional purchase into a defensible procurement decision — one your finance and leadership teams can approve quickly, without endless back-and-forth.

Conclusion: Building a Resilient IPv4 Procurement Strategy

IPv4 supply is no longer abundant, cheap, or forgiving of sloppy due diligence. The most resilient ISPs combine channels: they buy when prices and capital align, lease to absorb short-term growth, and keep verified marketplace relationships as a hedge against scarcity shocks. Whatever mix you choose, insist on documented ownership, clean reputation, RPKI readiness and professional escrow. Operators who institutionalize this discipline now will secure addressing capacity at predictable costs — while their competitors scramble during the next supply crunch. And there will be a next one.