IPv4 in 2026: What an ISP Actually Pays for Addresses, and What the Alternatives Cost

An ISP that runs short of IPv4 has three options: buy addresses on the transfer market, lease them, or share the ones it already has through CGNAT.

Each option moves cost to a different place. Buying ties up capital but leaves you with an asset you can resell. Leasing turns the cost into a monthly bill that never ends. Sharing costs equipment, logging and some support effort, but cuts the number of addresses you need by a factor of tens. This section compares the options over several years, explains how to get and announce address space today, and covers what sharing an address does to its reputation. Why the pools ran out is covered in IPv4 exhaustion.

EconomicsBuy, lease or share

The cost of an IPv4 address shows up as a purchase price, a monthly lease or a share of a CGNAT. Which one is cheapest depends on how fast your subscriber base grows and how long you need the space.

A fast-growing ISP that buys addresses pays up front for space it will only fill later. One that leases pays every month for as long as it exists. One that shares through CGNAT pays for servers and log storage, but each public address now serves dozens of subscribers. Most operators end up with a mix: public addresses for business customers and services, shared addresses for residential subscribers.

Buy, lease or CGNAT: the unit economics of an IPv4 address

Cost per subscriber over three to five years for each option, with every assumption spelled out so you can plug in your own prices, growth rate and sharing ratio.

IPv4 address prices: market data

How transfer prices moved by block size and region, and what drives them. Updated as new market reports appear, with the source and date of every figure.

What to do with IPv4 addresses freed by CGNAT

Keep them for business customers that need a public address, lease them out or sell them: what each option brings and what to check before you decide.

IPv4 TCO calculator

Compare buying, leasing and CGNAT over three to five years with your own subscriber growth and prices.

Address spaceGetting and announcing address space

Since the free pools ran out, address space comes from the transfer market and from waiting lists. It also has to be registered and announced correctly, or part of the internet will not reach it.

On February 3, 2011, IANA handed its last five /8 blocks to the regional registries. APNIC reached its final /8 two months later, RIPE NCC in 2012, LACNIC in 2014 and ARIN in 2015. In November 2019 RIPE NCC made its final allocation and ran out completely. Since then, an ISP that needs more IPv4 buys or leases it, or shares the addresses it already has.

How an ISP gets IPv4 space today: RIR policy, LIR accounts, transfers

Waiting lists, transfer rules between and within regions, and the paperwork each registry asks for before it approves a transfer.

Announcing your address space safely: RPKI, IRR and bogon filters

Route origin authorisations, route objects in the IRR and bogon filtering: the minimum routing hygiene that keeps newly acquired space reachable and hard to hijack.

IPv4 exhaustion in numbers

Remaining pools, waiting-list lengths and transfer volumes by region, updated from registry statistics.

ReputationIP reputation on shared addresses

When subscribers share an address, one abusive user can get everyone on it blocked or sent to a CAPTCHA. Blocklists and anti-fraud systems see an address, not a person, so a shared address inherits the worst behaviour of all its users.

IP reputation when subscribers share an address: bans, blocklists, CAPTCHA

How blocklists and large platforms treat shared addresses, how to limit the blast radius with sharing ratios and abuse handling, and how to get an address delisted.