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ARIN IPv4 Countdown Plan

Remaining IPv4 Inventory
Discrete Block Size (CIDR) Number of Blocks Available
View the block size distribution of ARIN's remaining IPv4 inventory at

Per policy, a /10 was reserved out of the last /8 to facilitate IPv6 deployment and that space is not included in our inventory count.

On 3 February 2011, the Internet Assigned Numbers Authority (IANA) issued the remaining five /8 address blocks in the global free pool equally to the five RIRs, and as such ARIN is no longer able to receive additional IPv4 resources from the IANA. Please read the IPv4 Depletion FAQ for more information on what this means for ARIN customers.

The ARIN community has worked together over the last several years in developing policy to manage how ARIN allocates and assigns IPv4 addresses. These efforts have extended the life of the IPv4 address pool in the ARIN region, but depletion of the IPv4 address pool is an impending reality. ARIN has reviewed and refined its procedures to create an IPv4 Countdown Plan explaining how IPv4 requests will be processed as the remaining IPv4 address pool is distributed.

PDF PPTX Webcast Archive
Presentation by Leslie Nobile, ARIN Director of Registration Services

IPv4 Countdown Plan - Currently At Phase 3

There are a number of variables that could accelerate or slow the rate at which ARIN moves through each phase.

  • Some IPv4 space may be returned to IANA in accordance with global policy
  • New policies and/or larger requests could change intended plans and lead to faster depletion of the remaining IPv4 address pool.

Note: Implementation of NRPM Fulfilling unmet needs is independent of and unrelated to the IPv4 Countdown Plan.

The Countdown Plan has four phases, and ARIN is currently in Phase Three:

  • Phase One began in February 2011 when ARIN received its last /8 from IANA.
  • Phase Two began in September 2012 when ARIN reached three remaining /8 equivalents.
  • Phase Three began in August 2013 when ARIN reached two remaining /8 equivalents.
  • Phase Four begins when ARIN reaches one remaining /8 equivalent.

Note: As ARIN moves through each phase, the current two-day response turnaround on requests may not always be met.

Phase One (February 2011 - September 2012)

    • A policy was triggered, reducing the IPv4 allocation window from 12 months to three (NRPM Section 4.2.2).
    • All IPv4 requests are peer reviewed. Larger IPv4 requests require senior analyst and/or department director approval.
    • IPv4 address space required for NRPM 4.10, which sets aside a contiguous IPv4 /10 block to facilitate IPv6 deployment, was reserved and removed from the remaining IPv4 address pool.
    • Returned, reclaimed, and revoked blocks are held for six months before going back into ARIN's free pool for distribution

Phase Two (September 2012 - August 2013)

[More Information]

    • Team review by senior analysts is used for /16 and larger requests. Peer reviews take place for all other IPv4 requests. Larger IPv4 requests require department director approval.
    • ARIN tracks all IPv4 request processing on a "first in, first out" basis (chronologically). This applies to handling of initial requests and all related response cycles.
    • Upon approval, all IPv4 recipients have 60 days to complete payment and/or a Registration Services Agreement (RSA). On the 61st day, ARIN releases the address space back to the available pool if payment and RSA are not completed.
    • The hold period for returned, reclaimed, and revoked blocks is reduced to three months.

Phase Three (Two /8 Equivalents Remaining, began August 2013)

[More Information]

    • ARIN staff examines processes used in Phase Two to ensure they are working and makes any necessary modifications.
    • The hold period for returned, reclaimed, and revoked blocks remains at three months.
    • Request reviews remain the same as in Phase Two, and requests for larger address blocks require department director approval.
    • Upon approval, IPv4 recipients have 60 days to complete payment and/or an RSA. On the 61st day, ARIN releases the address space back to the available pool if payment and RSA are not completed.

Phase Four (One /8 Equivalent Remaining)

    • ARIN reviews all IPv4 requests in the order they are received according to its timestamp. ARIN resource analysts respond to tickets as they appear chronologically in the queue. Each ticket response is treated as an individual transaction, so the completion time of a single request may vary based on customer response times and the number of requests waiting in the queue. Because ARIN processes each request in sequence, it is possible that response times may exceed the usual two-day turnaround.
    • All IPv4 requests, regardless of size, are subject to team review. Requests for IPv4 address blocks of /15 and larger require department director approval.
    • Once a request is approved, the requestor will have 60 days to complete payment and return a signed RSA (if applicable).  If payment and signed RSA are not received by the 61st day, the ticket will automatically close, ARIN releases the address space back into the available pool, and a new request must be submitted. This change to the approval window from 90 days to 60 days applies to all IPv4 requests, but not to IPv6 and ASN requests. 
    • The hold time before ARIN makes returned, reclaimed and revoked resources available for reissue is reduced from three months to 60 days.

A Note About Our /8 Inventory Counter

The counter shows the number of /8s remaining. The numbers after the decimal point are equivalent to a percentage (so 5.22 /8s is 5 /8s + 22% of a 6th /8). There are some days and even weeks where the total reported on the website won't change very much (if at all). Why? Because the threshold we need to cross is pretty significant. 1% of a /8 is more than 2.5 /16s worth of space. That's a lot of space to give out, and there will be some stretches of days or even weeks where ARIN does not give out 2.5 /16s worth of addresses.

Please be advised that the counter is for informational purposes only and is provided as-is. We strive to keep the information up-to-date and update the counter once a day. You however should not rely on the counter when making decisions on the timing of your requests for space. We suggest that if you require space that you submit your request as soon as possible.

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ARIN IPv4 space available: /8s in aggregate. Only reflects total available for allocation at this time

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