Mar 31, 2024 09:00:00

``Reverse DNS'' is a site where you can check at a glance who owns an IP address and how much.

Reverse DNS is a site that displays reverse lookup results for approximately 4.3 billion IPv4 addresses in a map-like manner.

Reverse DNS From IPv4 Space

https://reversedns.space/

This is what it looks like when you access the site. I can't tell what it is just by looking at it.

You can zoom in or out by scrolling. When you enlarge the upper left part, it looks like this. At the top left, the reverse lookup result of the IP address starting with 0 like '0.xxx' is displayed, but since the assignment to the user starts from '1.0.0.0', '0.xxx' is displayed. ” block is completely dark.

The blocks are arranged somewhat irregularly, with the '1.xxx' block to the right of the '0.xxx' block, the '2.xxx' block at the bottom left, and the '2.xxx' block. If you go to the right, you will see the block '3.xxx'. The address then advances to the upper right, and from there the structure repeats ``right'', ``lower left'', ``right'' again in

a fractal pattern .

Click on the map to display the reverse IP address lookup results for the clicked location. For example, the reverse lookup result for '3.21.194.0' is 'ec2-3-21-194-0.us-east-2.compute.amazonaws.com', which shows that it is an IP owned by Amazon. .

IPs owned by the same operator are assigned the same color. For example, IP addresses owned by Amazon are displayed in light purple, indicating that they own various locations like enclaves due to repeated purchases.

On the other hand, Google, another IT giant, mainly owns only a corner around '34.xxx'.

This is a remnant of the fact that IPv4 addresses were originally assigned on

a class- by-class basis; the area that used to be class A in the upper left is a relatively large piece of land, while the area that was class C in the lower right is a collection of small pieces of land. .

Also, for '10.xxx', a large black square appears because the entire block is assigned as a private IP address.

On the other hand, the 'land' of the private address '192.168.xx', which is often assigned by home routers, etc., is shown in the figure below. You can see at a glance that it is a very small area compared to the area in the upper right.

'I wonder if there are any Japanese companies...' I searched and found that Softbank had secured a fairly large area. In addition to Softbank, companies that started the provider business early, such as Comcast and Spectrum, seem to have large allocations.

In addition, the author has released

an explanatory slide on how to create Reverse DNS. This map started with obtaining the reverse DNS lookup results.

When we investigated all IP addresses, the domain that was most frequently registered in reverse DNS was 'net', followed by 'com'. 'jp' came in 3rd place, although it was one digit less than net and com.

Also, in terms of domains, 'amazonaws.com' owned by Amazon is the top, with 56.67 million IPs. In this ranking, the US provider comcast and Softbank's bbtec follow.

The author has also released the source code , so if you are interested, please check it out.