Vesna Manojlovic

RIR Prefix Size Distribution in RIPEstat

Vesna Manojlovic
Contributors: Christian Teuschel

5 min read

An alternative way of looking at the prefix size distribution in IPv4 and IPv6 blocks is now available in RIPEstat as an interactive widget. Tabular visualisation and cumulative percentage representation can be used for filtering based on minimum allocation size or for general research about the usage of address space.

Last week several operators on various mailing lists [ 1 , 2 , 3 ] expressed their need for prefix size filtering based on the minimum allocation size per certain address size block. The RIPE document ( RIPE-510 ) that some people previously used for this purpose has been replaced with a new version ( RIPE-555 ), which seems not to meet this need any more.

The data about actual delegations made by the RIPE NCC and all the other Regional Internet Registries (RIRs) is publicly available, so the operators can create their own methods to regulate the filtering.

Sizes and percentages

RIPEstat developers have created another visual interpretation of RIR  delegations data (PA allocations and PI assignments). It is an interactive widget called " RIR prefix size distribution ", in which you can query  for any address space prefix (0/0, 2000::/3 or 193/8, for example) and receive a prefix size distribution as an output.

193 slash 8

Figure1: Prefix Size Distribution for

You can use the resulting output to determine a cut-off point for filtering based on the minimum allocation size: for example, if the 193/8 block has only 1.34% prefixes smaller then /24 (or 103 in absolute numbers), you might decide that it is safe to not accept those prefixes. Or you can go for the /25 or /23 instead.

This is just "yet another view" of the distribution of prefixes. If you get curious, you might also want to see the graphical relationship of objects in the "hierarchy browser" :

86 slash 6 hierarchy Figure 2: 86/8 block as seen in Address Space Hierarchy widget



The "RIR prefix size distribution" widget also works for IPv6, but because of the huge size of the address space I included a smaller subset as an illustration here:

rir size ipv6

Figure 3: Allocations made from 2001:800::/23 IPv6 block


A subset of the output for the whole Global Unicast Allocations IPv6 space (2000::/3) is shown below, only the distribution of /48 to /32 prefixed, worldwide:

2000 slash 3 snippet Figure 4: A snippet of the table for 2000::/3


To Widget or not to Widget

As with all the other widgets, it is possible to embed this widget in your website: click on "embed widget" and copy the code.

The users can interact with the widget on your site and query for the resources they want, or you can choose to disable this and only show the results for the pre-defined query. More info in this article .

The specific link leads you to the feature of "one-page widget": only to this isolated widget, for only this kind of query. If you want to access all the other available information for prefixes and AS numbers, go to RIPEstat "proper":

Data call API

... and as for all RIPEstat widgets there is also a data call API available to be used in scripting and for creating your own favorite filters. Documentation is available here .


We are interested in your feedback:
- Do you find this widget & data call useful?
- How can we improve it, so that it suits your needs even better?

We already have multiple ideas for additional features in the next release of the widget, but we are very much looking forward to hearing from you and making a new widget or improving this one based on your comments!

There are several ways in which you can get in touch about RIPEstat:

We are also following many operators mailing lists, and are reacting to what we perceive as the needs of operators. Or we might meet at one of the NOG or IXP meetings after the summer.  And of course, see you all at the RIPE65 meeting in Amsterdam in September !

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About the author

Vesna Manojlovic is Community Builder at RIPE NCC. Vesna joined the RIPE NCC as a Trainer in 1999. In 2003, she took responsibility for developing and delivering advanced courses, such as RPSL, Routing Registry, DNSSEC and IPv6. In 2008, she lead efforts to establish IPv6 RIPEness as a measure of IPv6 deployment among LIRs. In 2011, she joined the Science Division as Manager of the Measurements Community Building team; in 2015 she moved to Communications Department as Senior Community Builder, with a focus on organising hackathons. Vesna gives presentations at many technical conferences and workshops, and enjoys visiting hackerspaces. Vesna received a Batchelor of Sciences Degree in Computer Science and Informatics from the School of Electrical Engineering, University of Belgrade. She has three children.

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