IPv4 Subnet calculator error networks /16

[simonecerbone]

Describe the bug

The network mask 10.0.0.0/16 is wrong beacuse the tool change the second octet in 10.1.0.0/16.
It has to change the third octet not the second.

What happened?

A bug happened!

System information

none

Where did you encounter the bug?

Public app (it-tools.tech)

[sharevb]

Hi @simonecerbone , I (and an IT friend) don't see any error in your screenshots. Could you highlight and give values you expect ? Thanks

[simonecerbone]

Hello, I’m attaching some photos for better understanding. Basically, when it comes to a /16, the first two octets (10.0.) are fixed, but if you click on the 'Next Page' button, it changes to (10.1.), which is incorrect since the /16 is 255.255.0.0.
The subnet 10.0.0.0/16 should change to 10.0.1.0/16, 10.0.2.0/16, 10.0.3.0/16... up to 10.0.255.0/16.

[sharevb]

Hi @simonecerbone, for me, what you expect is /24 not /16

[simonecerbone]

HI @sharevb , so, I don't quite understand the function of the "next block" button.
In a 10.0.0.0/16 network, the range is 10.0.0.1-10.0.255.254. To me, the "next block" button should display the next usable network, like 10.0.0.0/16 → 10.0.1.0/16.
Maybe I'm not understanding this correctly.

Thank you for the huge amount of work you put into creating this amazing site!!

[MisterHighping]

Hey @simonecerbone in that case it is like @sharevb described it.
You are thinking about an /24 network which would be 10.0.0.0-10.0.0.255 as a subnet or block (including the network and broadcast address). So the next block would be 10.0.1.0-10.0.1.255 and so on.
In case of a /16 network the last two octets are part of the subnet or block. Like you said 10.0.0.0-10.0.255.255 is the first block.
So the next one is 10.1.0.0-10.1.255.255 because within each network there are 65536 IP addresses before the next block starts.