Weird IPv4 connotation, did you know?

Pilzbaum

Hey guys,
today I came accross some interesting stuff regarding IPv4 connotation. I tried to come up with an ugly IPv4, that surprisingly wasn't a correct IP address. At first I didn't know why, but after some reading I understood. If you want to give your knowledge about IPv4 connotation a try, I attached a poll with one real and several fake IPv4 addresses. You can see an explanation to each address of the poll and the solution in the spoiler below.

As I found out, IP address can be written with decimal, octal and hexadecimal connotation for each block in any variety. I think it's a bit strange that it doesn't work with binary, but it is what it is. Octal blocks need to start with 0 and hexadecimal blocks with 0x. Now lets get to my examples.

1. 010.059.08.0x088
   This one could be a potential winner, if it wasn't for the 059 and 08 part. The leading 0s indicate an octal number which can only contain number 0-7. The 0x88 is a perfect valid IP block tho (136 in dec).

2. 0010.0001.0003.0001.0222
   This one does indeed contain only valid numbers smaller than 255 in decimal, but it's one block too long. IPv4 addresses consist out of maximum 4 blocks divided by dots.

3. 127.253.079.151
   This address was the one I came up with in the beginning. I was quite surprised, as I really thought it was valid, but 079 indicates an octal. Without the leading 0 it would be a perfectly fine example of a loopback ip address.

4. 0x7F.023.0012.0262
   This one is the winner! While it looks abnormal, this IP represents 127.19.10.178.

5. 0177.00221.075.0x188
   Here the problem is the hexadecimal 188 which is a 392 in decimal. Therefore it's invalid.

6. 10.47.258.31
   This should be quite a simple one. No tricks regarding octal or hexadecimal, only plain decimal. But 258 is greater than the maximum of 255.

7. 127.0xFFFFFE.12
   While it does look odd, 127.0xFFFFFE would be the valid hexadecimal representation of 127.255.255.254. This could be quite useful for programming stuff. However, with the added .12, it is invalid.

I hope you had fun!

Pilzbaum

Sorry, edited the post and deleted the poll accidentally. I hope I fixed it again

Shot2

What about 076.0xD2.2

Pilzbaum

At first I thought that it shouldn't be, as the part without delimiters (meaning dots here), should be at last, imo. But then I checked, and it is indeed valid.

The reason for this is that 0xD2 (210 in dec) can perfectly fit somewhere in between blocks, however, if the hexadecimal number is greater than one block (>255), it needs to be the last block.
Examples:
076.0xD2DA.2 is invalid, but
2.076.0xD2DA is fine

Thanks @Shot2

SGraf

just** for fun**...

go ahead and ping 1.1

enjoy

Pilzbaum

@SGraf I believe this one could even tell me names

jsg

Funny, interesting read, thanks.

TimboJones

This dude must not have a TV.

Actavus

@TimboJones said:
This dude must not have a TV.

No. He has internet.

Pilzbaum

Well, I have got no TV. Definitely correct.

Anyway, the reason why I came up with this was because of a friend. I was chatting with him and tried to find one of the ugliest IPv4 addresses possible. After some experimenting, I came up with 127.253.079.151 and tried to ping it. "Name or service not known". I was totally confused, but after some research, it became clear why it's not possible.. Anyway, later on, I started to experiment a bit more and crafted some nice looking (invalid) addresses for the post.

I think it's quite sad, that binary numbers are no option tho.