Why Is Your ISP Using Reclaimed Ipv4 Addresses Instead Of Switching To Ipv6?

Internet Protocol addresses allow computers, mobile devices, smart appliances and more to connect to the Internet. IP addresses also identify websites. Each server or device has its own four-part numerical address assigned by an Internet Service Provider (ISP), which gets a block of available addresses from the American Registry for Internet Numbers (ARIN).

The problem with this four-part number system is that, as of July 2015, there are no more unused IPv4 addresses that ARIN can assign. Because IPv4 uses 32-bit addressing, there are 4.3 billion possible combinations -- and those are now all in use or have been purchased by ISPs for use.

Purchasing or Leasing IPv4 Addresses

Because there are some organizations that have excess addresses that are not yet in use, a market has emerged for people to buy and sell these IP addresses. If an ISP is interested in getting more IPv4 addresses, there are three main options:

  • Get on ARIN's wait list for available IPv4 addresses that come available as ISPs give them up (rare) or go out of business. 
  • Purchase IPv4 addresses from a company that is not using them and does not plan to.
  • Lease IPv4 addresses from a company that is not using them currently but wishes to retain ownership in case they are needed in the future.

Some IP addresses have greater value than others. For example, a block of addresses that was used by a reputable email service and then made available for sale would be more valuable than addresses that had been used to send spam messages. When you use new IP addresses from your ISP, it may be useful to find out where the addresses have come from and what they were previously used for.

Many ISPs are using ARIN IP brokers to buy, sell and lease unused blocks of IP addresses. These brokers can help connect buyers and sellers and get the required approval of ARIN for the transfer of ownership of these address blocks.

Implementing the New IPv6 Protocol

The other option for ISPs that need more IP addresses is to switch to a new naming protocol known as IPv6. Instead of 32-bit addressing, these use 128-bit addressing, which provides enough addresses for every atom on the planet -- roughly 340 trillion trillion trillion options. It seems unlikely that we could ever run out of IPv6 addresses.

The problem with IPv6 addressing is that it is not being adopted quickly. Current technologies that ISPs use to name their servers and other devices, known as Network Address Translation (NAT), allow one IP address to be used for several machines and are fine with the IPv4 system. But it will take time and money for new equipment to implement IPv6, and many ISPs don't want to make the investment. It may be months or, more likely, years before IPv6 is more widespread.

Right now, most ISPs are finding that it makes the most sense and is most cost effective to purchase unused IPv4 addresses from IP brokers who specialize in this service.