ARIN Utilization and Leased Space: What Counts

By Savvas Bout, Founder of Prefixx. Last updated 6 November 2026.

For organizations in North America considering IPv4 purchases , or looking to lease IPv4 addresses for short-term needs to supplement current addressing space, understanding the rules for ARIN recognized utilized space and the impact of leased addresses is key to maximizing potential transfer options.

ARIN recognized utilized space is used by the registry to determine if an organization would benefit from the addition of new IPv4 address space, for purposes of considering a transfer. The amount of address space an organization is granted.

Additionally, As a factor influencing negotiations. Leased IPv4 address space does not necessarily pass the needs basis review by ARIN and the lines of operational use of rented addresses versus mere utilization can have significant impacts on how transfer approval is handled by ARIN.

In this article we’ll examine the different ways that ARIN measures address space utilization, how leased space affects this, and provide information for network engineers and IPAM practitioners so that they can better understand the implications for transfer requests as well as potential lease agreements.

What ARIN utilization means and why it governs every allocation request

Utilization refers to the efficient use of IP IPv4 block that an organization currently holds. In order to obtain new IP addresses (i.e. resources) from the American Registry for Internet Numbers (ARIN), the organization must provide evidence that the space they currently have is being used. This would apply to an ISP’s allocation as well as to direct assignments for end-users.

The thresholds that govern new requests

Additional space requested by ISPs is reviewed by ARIN under an 80% utilization threshold. In other words, 80% or more of an ISP’s current allocation must be actively assigned before a follow-on request for additional space will be considered.

Initial allocation request follow a different time frame. Each organization must demonstrate 25% utilization immediately and provide a reasonable plan to reach 50% utilization within 12 months. Each request must meet these criteria before ARIN can approve the request.

This new draft policy, ARIN-2025-1, raises the bar even more. This new criteria that must be met by an applicant for a special allocation of IPv4 numbers is listed below.

• 75% utilization of total IP block across the org ID.
• More than 90% utilization at any single serving site.

Both conditions must be met to declare a server cluster as passing load tests.

Does leased IPv4 space count toward ARIN utilization?

This is an area where many organizations incorrectly assume ARIN only counts used space against registered space for an organization ID. Space leased in this manner is registered in the lessee’s name, not that of the lessor, and thus will not reflect in the lessee’s utilization.

The impact of leased space is that it does not count towards demonstrating consumption of space that will be used to justify new space allocations. Space held in leased space only counts if it is held in an ARIN registered space of your own. This is something to verify with your routing consultant before embarking on a growth plan based on leased blocks of space.

What a justified idea means in practice

In reality, ARIN looks at the actual assignments of IP space, not the projections that an organization makes. For a request to be considered justified, documentation needs to prove that there is real, routed end-user traffic on the space that an organization currently uses.

Unrouted or “parked” IP addresses do not count toward utilization, regardless of how they may be listed in an organization’s WHOIS records. This information helps to grasp how ARIN counts numbers for utilization. Organizations should maintain detailed records that allow them to clearly demonstrate and view how each assigned block is actively supporting operational traffic.

How ARIN utilization and leased space factor into calculations

ARIN considers used address block to be utilized by a organization for which it has downstream needs and for which it is actually being used by that organization or for which there is other active use by the organization.

To determine how leased space would be treated under the policy, it is helpful to know what space ARIN considers to be used, what space ARIN does not consider to be used, and what documentation would be required to issue additional IPv4 number space to an company.

What counts as requested and utilized address space

Assignments of space by an ISP to use (reassign or sub-allocate) for documented needs (genuine requirements) of a customer count toward utilization of leased addresses.

Reserve space that is not actively assigned to connections does not get counted. Even if addresses are technically allocated, ARIN does not consider space that is holding idle addresses to be utilized. Space that has been requested by a customer but has not yet been deployed counts against utilization.

The swip and rwhois requirement for internet services

Reassignments are reported by ISPs to ARIN via SWIP (Shared WHOIS Project) or via an RWHOIS server. Each reassignment contains information regarding the IP addresses that were reassigned (such as an IP address range) as well as the corresponding Org ID and end user. The registration services team at ARIN has a verifiable audit trail of such reassignments. The audit trail ensures that all reassignment records can be retrieved and messages sorted by date or organizational identifier for verification purposes.

Space leased but no SWIP record created typically does not get counted towards utilization. Remember that the ARIN auditors review the IP registration information. A legitimate address not showing up in the review of paper copy or online domain registration information will not get counted towards the company’s utilization figure.

What utilization percentage does ARIN require before issuing additional IPv4?

For ISPs and end users requesting directly, ARIN requires utilization of the currently allocated space of at least 80%. Requests for space less than this block size are denied or awarded at a less than requested size.

Leased space that needs to be counted against an upcoming allocation request should have current SWIP records prior to the review date for the allocation request. LOA, RPKI ROA, and IRR route objects are prepared as part of the lease for space, including reassignment documentation for a clean ARIN utilization audit.

The utilization rules at ARIN are enterprise type specific, i.e. ISP allocated space versus direct end-user space. How the rules translate is different for each business type. Organizations should confirm that their routing consultant can provide guidance via phone or email regarding the proper documentation sequence for reassignments.

Direct assignments versus ISP allocations: different utilization rules

ARIN differentiates between two types of recipients. The line drawn between them will often dictate how utilization will be measured, what constitutes justified use of space, and whether or not renting out space to a third party will count toward future requests.

Allocation based versus direct assignment

1. Determine if the recipient is an ISP (given a block allocation, they then sub-allocate to their customers downstream). Alternatively, An end user (assigned space directly that they will utilize within their own firm and report used within that entity). Utilization for a block of space is calculated cumulatively across all customer assignments within that block of space.
2. Document Requirements for an ISP or End User justification are based on two main categories of evidence, Customer Assignment Records and End User’s Internal Network. The type of documentation required to complete a justification for an ISP versus an End User differs and therefore it is essential to verify the customer classification prior to commencement of the completion of the justification.

Note: An end user cannot lease out space to third parties and count those external assignments as utilization for a new direct assignment request. ARIN evaluates use within the requesting operator's own infrastructure.

Qualification for micro allocations in critical infrastructure

1. The carve-out for such critical infrastructure operators (including core DNS service providers and public peering exchange points) is provided via special micro allocations subject to their own size and justification criteria separate from that used for standard ISP and end-user allocations.
2. Your justification must establish the special nature of your use of IP address range as infrastructure. We do not accept standard end-user application forms or documentation. You should contact ARIN by email before submission of an application to confirm the appropriate form and required supporting documentation.

Can an end user lease out their arin-allocated space to a third party?

No, in general direct assignment holders are expected to utilize the space allocated within their own infrastructure. Thus renting out space to external parties does not constitute utilization under ARIN ’s method of measurement and therefore will not enable a follow-on request for more space.

Sub-leasing of space would be done as an allocation-based ISP and Prefixx can help to determine whether you are an allocation-based ISP or not prior to your submission. Next would be the required legal agreements between you and ARIN to issue or transfer allocated IP space.

The RSA, the LRSA, and what you sign before ARIN issues space

Before ARIN can assign an IP address range to an provider, the service provider must execute a legal agreement that specifies the terms and conditions under which that registry member will use the IP addresses and related resources. It is very important to comprehend which agreement(s) apply to an address holder, and the commitments and conditions in such agreements, before submitting a request for assignment of IP addresses or a transfer of IP addresses.

The RSA and what it covers when receiving aid

New resource holders sign the RSA (Registration Services Agreement) which puts them under the current ARIN policy for new resource holders. Subsequent requests from a resource holder are subject to utilization review for all new requests for space. ARIN will seek information on how space already allocated to a resource holder is being utilized prior to making additional space available. The RSA is intended to be the basic contract for new allocations by ARIN.

The ability to sign an agreement online also enables inter-RIR transfers. Until an executed copy of an agreement is placed online (e.g. at www.ARIN.net), ARIN cannot process an outbound transfer or an inbound transfer (pursuant to the Number Resource Policy Manual).

Legacy space and the LRSA for internet services

Space that was assigned as pre-RIR legacy blocks (i.e. before the regional registry system for IP addresses was put into place) is outside of the standard terms and conditions of the contract with the RIR. However, legacy holders of such space can agree to be bound by the Legacy RSA which enables them to be covered by current RIR policy whilst still retaining their legacy status in full.

In contrast, holders of pre-RIR legacy space who have not signed up to the Legacy RSA are subject to a different set of rules regarding transfer and use of their space. Typically, their IP lookup contact information is not fully structured and thus not compliant with modern policy requirements. Additionally, such space is generally not transferable between RIRs until an inter-RIR transfer agreement has been put in place.

Legacy space without an LRSA is typically unable to participate in ARIN-facilitated inter-RIR transfers. Signing an LRSA will resolve this and bring the record up to current routing hygiene expectations.

What is a swip record and why does it matter for utilization reviews?

SWIP (Shared WHOIS Project) is the way that ISPs document downstream reassignments in the ARIN database. For example, if an ISP takes a /24 out of a larger allocation and assigns it to a customer, the SWIP record for that /24 would list the customer's name, address, etc.

When we conduct a utilization review, we use SWIP data to verify utilization of allocated space. If no downstream SWIP records exist for a block of space, or if the records for a customer are old and refer to a customer that is no longer active, then space that has not been fully utilized can impact a subsequent request. Thus, keeping current SWIP records serves as irrefutable proof that services are being delivered over the allocated space.

As part of the Tixx quality control for Prefixx, SWIP hygiene reviews for every block are conducted. Having clean and up to date records helps reduce friction from the time of a first inquiry right through to sale or lease of that block of IP addresses. The friction will only increase as ARIN’s free pool of IP addresses dwindles and the only way to get additional IP addresses is via the secondary market for IP range.

The ARIN waitlist, free pool exhaustion, and the secondary market

After ARIN’s free pool of IPv4 addresses reached exhaustion in 2015, the methods by which ISPs, end users, and enterprises obtain IP addresses to connect to the Internet to have changed. Now, allocations are not issued immediately by ARIN.

How your requested spot on the waitlist works

After ARIN’s free pool of IPv4 addresses reached zero, ARIN began maintaining a waitlist for organizations needing IPv4 addresses. Data shared at the ARIN 50 community meeting provided insight into the growing list of waitlist requests (approximately 120 per quarter) with less than 60,000 addresses available in total.

For example, a single /16 block has room for 65,536 unique IP addresses. The total remaining in the ARIN pool is less than a single medium-sized allocation. People on that wait list have no way of knowing how long it will be before their turn comes or if they will get an assignment at all.

Why core DNS service providers drive the secondary market

By 2011 all five of the RIRs had used up their free pool of IPv4 addresses. IANA’s central pool of IPv4 addresses had already been exhausted by that time. As a result of the lack of supply from the registries, today's client organizations needing IPv4 addresses have to purchase them from current holders in the form of a transfer or a lease and not as an allocation.

Two types of acquisition are now standard:

• Transfers: permanent sale of a block, recorded at the relevant registry.
• Leases: time-based usage rights, with the original holder retaining registration.

We at Prefixx are brokering both paths.

What happens to a lease agreement when the block is transferred to another RIR?

An inter-RIR transfer of a block of IP addresses changes the registration of the IP addresses to another IP address registry. All existing leases for the IP addresses are based on the original registration of the IP addresses.

When a block of IP addresses is transferred between IP address registries post-lease, during the middle of an active term, the conditions of the agreement must be renegotiated with the new IP address registry's policies.

So, lessees should verify the registry jurisdiction for any block offered for lease on a transfer-ready basis before entering into a long-term lease of that block. The distinction between a lease and a full transfer of registry for your ARIN-region network of IP addresses and related resources is critical here.

How leasing IPv4 fits into an arin-region network without triggering a transfer

Note that leasing out IPv4 addresses and transferring them out are two different things legally and operationally. This is something to keep in mind when you’re an ARIN region network engineer trying to decide between leasing something to fill in some short term space vs. buying it to own it forever.

What changes in ARIN WHOIS, and what doesn't

A lease does not change the information in the ARIN registration records. The original org ID is the registrant for the space leased. Lessee gets a Letter of Authorization to announce the space under their own ASN using BGP. registration database ARIN information continues to display the lessor for the term of the lease.

On the other hand, a transfer is the reversal of an assignment. Ownership is moved from one IP holder to another, and the registration record is updated to reflect the change. The acquiring registrant is then assigned a new allocation with their own subscriber ID. The transfer of registration is done through ARIN’s registration services and the block is reflected in the new registrant’s IP registry record after the transfer has completed.

Do I need to sign the RSA before ARIN will approve a transfer request?

ARIN requires that the transferring account holder and the receiving member be “in good standing” and that both have signed the Registration Services Agreement (RSA). Legacy resource holders with resource listed under an LRSA also must have a signed copy of the RSA agreement. Transfers will not be processed by ARIN regardless of the size of the IP addresses to be transferred if this agreement is not in place.

RPKI ROA issuance in a lease context

The resource holder also keeps registration for ROA issuance. In order to maintain routing security, the holder of resources has to authorize the lessee’s ASN in the ROA. The announcement of the lessee will otherwise be declared invalid by RPKI-validating networks.

Leases are ideal for short-term needs for space that you won’t own, and Transfers are ideal for longer-term control of IP pool plus a clean ARIN record under your own org ID. Prefixx can support both paths to acquiring space online. The policy rules governing these two methods of obtaining online space are not static and thus are best kept up-to-date via the ARIN community process for submittals.

Previous message by thread: how ARIN policy discussions shape utilization rules over time

ARIN’s policies are developed by the community, go through public comment before being ratified. Additionally, The policy in effect on the day a request is submitted is the policy that will be used to approve or deny that request. Knowing how the process works and how to research the history of a policy can give you a big edge before you actually submit a request.

Next message by thread: finding the policy trail

The Public Policy Mailing List (PPML) archives all of the discussions that took place on a particular proposal. Each message in the archives includes links to go forward and backward in the conversation. The link to the previous message by thread is especially useful to see what the proposal looked like before people started commenting on it.

1. Find the proposal in the PPML archive. Look up the draft number for the proposal in question, e.g. ARIN-2025-1. The opening post for that draft contained specific language around utilization thresholds: 75% of total space allocated and greater than 90% of space allocated for any given serving site.
2. Go back a step in the thread. Click on the Previous Message by Thread Link to review the earlier messages in the thread, such as a premeeting discussion or the proposal that this draft was based on. This helps you recognize what led to the community’s reaction to the current version of the document.

Reading the requested debate forward

1. Just follow the next message in this thread to see how individual operators, ISPs and their staff members handled the threshold language in question. Occasionally, an objection here is removed in a revised version before it is ratified.
2. In addition to viewing a thread, messages within that thread should be sorted by date so the peak of recent activity (e.g. where a major revision was made or a question cleared up by staff) is visible.

Note: A proposal can be amended after the meeting but before the Board vote. Always read the final ratified text, not just the draft you found first.

Applying what you read before you submit

1. Make sure to confirm the current threshold. ARIN-2025-1 is a live document that continues to evolve with threshold language. Verify what version is current when you prepare your request as ARIN reviews your resources against the policy that is current on the day you submit your request.
2. Check if the space that you lease qualifies. The community had a good debate on this issue with ARIN-2025-1. Read the ratified text carefully. Leased space may not count towards your utilization so even though you are fully loaded, your allocation request may not meet the threshold.

Prefixx reviews with clients the documentation for utilization of assigned blocks prior to submission. Leased space can present a number of policy issues with respect to inclusion in a block mix for example, only utilized space under current ARIN policy would be included in a request for that space. We note similar restrictions with regard to movements of blocks entirely within the registry of service of a Registry.

Inter-rir transfers and what changes when an ARIN block moves registries

Transferring a block of IP addresses across registry boundaries is one of the most complex transactions in IPv4. Because the rules governing a block of space transferred from ARIN-regulated space can be quite different from those governing the same block of space in the destination registry, complications in the middle of a lease can easily scuttle even the best laid plans if the requisite documentation is not appropriately constructed at the outset.

How policy jurisdiction shifts on transfer

The utilization policies of ARIN no longer apply to a block of numbers once that block of numbers has been transferred between RIRs in an inter-RIR transfer. Once numbers have been transferred to a destination registry, they are subject to the allocation and assignment policies of that destination registry.

For example, numbers transferred to the RIPE NCC in an inter-RIR transfer are subject to the allocation and assignment policies of the RIPE NCC, not to the needs-basis utilization policies of ARIN.

For approval of an outbound transfer, the transferring stakeholder must fulfill the requirements of Section 8.3 of the NRPM, as specified by the transfer policy.

Supported paths and lacnic's special status

ARIN supports direct inter-RIR transfers to RIPE NCC and APNIC. While both registries have bilateral agreements with ARIN that detail procedures, timelines and eligibility for such transfers, the most common path for service providers looking to go to Europe or Asia-Pacific is through RIPE NCC and APNIC transfers.

LACNIC does not have a direct transfer agreement with ARIN. The transfers of LACNIC address pool are facilitated by the membership and not part of a standard bilateral agreement between two RIRs. The differences in these types of facilitated transfers versus a standard bilateral transfer need to be considered in terms of the time frames and documentation required.

Leased space and LOA validity during a transfer

An active leased block can’t be transferred mid lease without the lessee agreeing to the transfer. The lessee retains the routing for the lease term. Any attempt to transfer the registration of a block without the qualification of lessee consent creates a conflict with the new registry entry and the contractual routing authority of the lessee.

An LOA issued at lease origination is automatically terminated when a block changes to a new registrant or a new registry. A new LOA must be issued for the new registration details in order to continue announcing the prefix by the lessee.

Rebuilding LOA, RPKI ROA and IRR route objects for a transferred leased block of IP address inventory requires re-registration of the updated objects under the new holder of the LOA. This re-registration can be coordinated with the renewal of the underlying lease to minimize the time during which there is no authoritative routing information.

Prefixx holds registered broker status with ARIN, RIPE NCC, and APNIC. Our team prepares the full transfer package, including the LOA, RPKI ROA s, and IRR route objects, coordinating with both registries so nothing is left outstanding. For inter-RIR transfer support, visit Prefixx.net/IPv4-transfers. Once the transfer paperwork is in order, the next practical step is qualifying your end user for any additional ARIN space you need alongside it.

Qualifying for additional ARIN space: a step-by-step utilization review

Qualifying for additional IPv4 space from ARIN is more than just filling out a form. All current allocations as well as the domain registry information for an user are analyzed by the qualified analysts who verify growth information for proposed new space before it can be assigned. Organizations with clean records and good record keeping of growing demand are rewarded.

Audit your current allocations and swip records

Begin by querying all of the allocations and assignments associated with your org ID from the ARIN registration lookup database. For each of the reassigned subnets verify that there is a current SWIP record. Leased and reassigned space will only be credited by the ARIN analysts for the actual end user, not the holding client.

ISPs with /20 allocations that have reassigned /24s to customers must ensure that IP ownership for each /24 contains the name, address and contact information for that customer.

Calculate utilization and build the growth justification

ARIN applies a utilization threshold prior to approval of additional space. For most ISPs this would be 80% utilization of the current allocation(s) being adequately justified as currently in use. End users would be subject to similar thresholds for space assigned to them.

Document your 12-month growth projection with details about new customers, planned infrastructure, and how subnets will be allocated.

Submit via ARIN online and respond to analyst review

Log into ARIN Online using your org ID and submit a resource request of the appropriate type (i.e. ISP additional allocation or end-user assignment request). The request can include attachment of your utilization summary and associated growth documentation in one step.

Analysts typically follow up with specific questions.

Our consultants at Prefixx have recently prepared the supporting documentation (including LOA and routing information) for a number of blocks recently sourced via the transfer market.

Why Prefixx for arin-region IPv4 leasing and transfer support

Prefixx is a registered broker with ARIN, RIPE NCC and APNIC. For organizations that immediately need allocated IP inventory, we source the best vetted ARIN allocations and handle all the necessary routing paperwork including LOA, RPKI ROA and IRR route objects for immediate announceability of your prefix.

• Quality control on every block of Tixx. Ownership, transfer eligibility, black list status, and routing quality are checked before any allocation is released to lessee or buyer.
• Non-revocation lease guarantee. Written commitment with 24 hour end user provisioning.
• Zero buyer fees. Sellers pay a 3 to 8% commission. The buyer pays nothing.
• Inter-RIR transfers handled end to end. ARIN, RIPE NCC, APNIC, and LACNIC (facilitated) resources are all in scope. Learn about inter-RIR transfers.
• White-glove included. Our team manages geolocation correction, reverse DNS, reputation monitoring, and abuse processing for every leased block. See lease options.

We have consultants ready to assist you to quickly qualify your needs and match you with the appropriate allocation (ARIN numbers quickly, inter-RIR transfer request submission). Compare options here.

Key takeaways: ARIN utilization, leased space, and the transfer market

IP address utilization and leased space sit at the center of every allocation decision the American Registry for Internet Numbers makes. ISPs and end users must demonstrate justified need before ARIN will issue IP resources, and leased prefixes count toward that utilization only when properly documented through SWIP in domain ownership.

Direct assignments to customers, micro allocations for public exchange points or core DNS service providers. Additionally, Standard assignment-based requests all follow the same rule: show the registry for internet numbers that your customer has used what it already holds.

The secondary transfer market exists because IANA exhausted the free pool and ARIN followed. End users who cannot qualify for a new block turn to that market instead. Leasing provides routing rights, not registration, so a valid LOA and ROA remain required. Inter-RIR transfers move resources outside ARIN policy entirely.

ARIN's utilization rules are strict by design. Every address block request, whether for new space or an expansion, lives or dies on your ability to document warranted need, and leased addresses count only when the lease is arm's-length, properly documented, and verifiable.

The free pool is gone. For most organizations, the secondary market is the practical path to address resources today, and the Registration Services Agreement or LRSA is the agreement that governs whatever you hold once you have it.

If you need a vetted ARIN block, want to identify what your existing space is worth, or need a lease structured to satisfy ARIN's documentation requirements, Prefixx handles the sourcing, transfer paperwork, and routing setup end to end. Reach out to start a conversation.