#Technology & Innovation

IPv4 Address Brokers and Legacy Address Space

If you are the contact listed in one of the global registries for the IPv4 addresses held by your University or College, I’m sure you will have received numerous emails from address brokers offering to buy some or all of your IPv4 addresses. This post is intended to provide some advice.

Many of Jisc’s members have substantial amounts of IPv4 address space, some of which may have been allocated under various different regimes.

First there are ‘legacy’ or ‘early registration’ address blocks. These were allocated by the Internic before the introduction of the Regional Internet Registry (RIR) system in the 1990s, and were typically allocated directly to the university. These are usually referred to as a ‘Class B’ or a ‘Class C’ as they dated from the days when Internet routing was classful.

Second there are ‘provider aggregatable'[1] addresses. These were assigned by, depending on the time of assignment, UKERNA, Janet, or Jisc, operating as a Local Internet Registry (LIR) within the RIPE NCC, the RIR for Europe and the Middle East.

There is a third type of address, ‘provider independent’ addresses that are used much less frequently on Janet, but for these purposes are similar to ‘legacy’ addresses.

Whilst the second type of address is assigned only as long as the original criteria for assignment hold true, and must be returned to Jisc’s pool of available addresses when this changes, the former were effectively allocated in perpetuity and are often seen as belonging to the institution in question.

There have been various dates in recent years that have been trumpeted as the “end of IPv4,” but regardless of that the number of free IPv4 addresses within the RIR system is low, and as it is no longer possible for Internet Service Providers (ISPs), Cloud Service Providers (CSPs) or Content Delivery Networks (CDNs) to get new IP addresses from the RIRs, they are increasingly buying them in the growing IP address marketplace.

This means that legacy addresses have a value, and address brokers have for some time been approaching Jisc’s members offering to sell their IPv4 addresses for them. A recent email offered “up to” US$1.3M for a /16 (by the time I publish this, that’s probably ~£1.3M).

At least two of our members have sold some IPv4 addresses, which is entirely legitimate, but we would like to provide our members with some advice.

Jisc cautions our members about accepting offers that come from unsolicited emails, especially from brokers based outside of the EU, and if address sale is something of interest, we suggest approaching brokers that have agreed to abide by the relevant RIPE NCC policies:
Note that listing on that page is not a recommendation.

The RIPE NCC’s Frequently Asked Questions page for transfers is here:

To understand the terminology on that page, much of the early registration address space is registered with the RIPE NCC with Jisc acting as a sponsoring LIR.

Please remember that ‘provider aggregatable’ addresses assigned by the Jisc/Janet LIR function may not be transferred to a different provider.

Of course the value of IPv4 addresses may fall as well as rise, and it will certainly do the former as the deployment of IPv6 increases and the need to use IPv4 decreases. Many large CDNs, such as the one used by Facebook, use only IPv6 internally and only use IPv4 for the externally-facing load-balancers and proxies. Jisc members should, however, consider carefully what their usage of IPv4 addresses is likely to be over the coming years, even if using Network Address Translation (NAT), as a greater number of devices on private addresses requires a larger pool of public addresses to ensure session stability.

Jisc maintains a reasonable supply of IPv4 addresses that can be assigned to our members on request, subject to the rules of the RIPE NCC. Usage of historical assignments and the planned utilisation of addresses are part of those rules.

[1] Whilst it should be ‘aggregable’, the resource documents almost all use ‘aggregatable.’

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