Is there currently a formula for calculating the network ID when you know the amount of networks used?

Question

**edit: I wanted to mention the reason I am asking is because I have scoured the internet to find a formula similar** I figured a formula and wanted to know if such a formula is was already in use. (256/number of networks) * (desired subnet - 1) Edit: the use of 256 is one over the max number used in ip addresses. Edit: 256 isn't the largest possible network in the formula. It creates the decimal quotient used to predict the ip address for that subnet. If the result after the formula is a decimal then multiply that decimal by 255 aka the max number of ip addresses in an octet which will show the number for the next octet.

Answer 1

I am personally not familiar with that formula but the one I am familiar with is the following, which does require the subnet mask to be known:

Something called the logical AND, which is what Cisco teaches in their Netacad platform. AND here is a Boolean Algebra operation where 1 and 1 equals 1 but 0 and 1 equals 0.

To accomplish this you turn both the subnet, which can be written as 255.255.255.000 for example, and the IP address of the host, which can be like 193.17.21.3, into binary numbers. So binary is made up of just 1s and 0s.

Once you have both numbers into binary, then you AND them.

Once you accomplish that, you turn that result back into a number using the decimal system.

When subnetting the network, information you can be given is what the network is that you are using so let's say the company owns 193.15.17.0 and they own that entire last octet. They want to subnet so then the network won't have too many left over devices. Let's say one network will have 25 devices but the other is going to have 100. In the end both subnet masks will even be different and so will the network.

For me to figure something out like this, I don't really use a formula but instead think of which subnet mask will allow 25 devices without too many devices being unused. I know that 255.255.255.000 which is a /24 allows 256 IP address which 254 will be host IP addresses since one I need to leave to be the broadcast address and the other one will the network address. /25 subnet mask will give me 128 addresses (126 host IPs), /26 will give me 64 addresses (62 host IPs), /27 will give me 32 (30 host IPs), /28 will give me 16 (14 host IPs), /29 will give me 8 (2 host IPs), and /30 will give me 4 (2 host IPs). People typically don't subnet out to /31 and /32. I can see that the /27, which the subnet mask is 255.255.255.224, allows me 30 host IP addresses which is not too much over 25. /28 only gives me 14 host IPs, which is too little of a number for me. So I know in the end the subnet mask I want will be a /27, which means the network address can be a 193.15.17.0 and the broadcast address would be 193.15.17.31. The /27 also gives you 8 networks unless one of the networks we even subnet further then the entire number of networks that companies has is even more but then the subnet mask for that particular network will not be a /27.

When determining network ID, I would say important information to have is not the number of networks but the subnet mask and the IP address of the device you are working with.