This question was marked as "off-topic" :
The reason stated was :
Unfortunately, education, certification, or homework questions are off-topic here. There's plenty of learning sites on the Internet. This one isn't one of them. In real world we don't use such large networks.
But _ar provided an interesting answer.
Before asking I did some research, I understand how network addresses and masks works. So I supposed that it was not possible to divide a network into one quater for the first subnet, and the rest in another subnet. But as I'm not a network engineer, I asked here if there is a solution to this.
This is a company network. I'm planning databases migration, and yes, this will be enterprise subnets. There will be a few thousands IPs in each subnets. First I start with 2 networks that the network team gave me, then I divide it.
How is this not professional ?
In JFL comment, stated as a reason :
In real world we don't use such large networks.
First you divide a network into subnets, then you you have smaller subnets. And I could have given an even larger network as an example, since this can be viewed as a theoretical question (but applied to a real enterprise network). The first choice was to use 10.0.0.0/8, then divided it in /16 , then again, then again...
Unless questions about sub-networking are not valid here ?
I suppose JFL was referring to (Help Center):
installation, configuration, or use of applications not generally considered to be tools used by network professionals;
Which cannot be the case here, every network engineer has to do these kind of things when they're starting to design their networks ?