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Note-:Here, IP address means IP address+subnet mask.

I am studying network design. My question is will there be a moment where you choose IP address for subnetting but turns out finally that it's insufficient(Not in future, just in present).

The question is better worded as "how to choose IP address for subnetting?"

My question would be how would you decide what network id and what host id aka what class of IP address you should choose for subnetting for different amount of hosts? (I know classes are gone, I am just using it for the term host id and network id, and I also know number of hosts are determined by /## term I am just using it for ease to understand).

For eg-: say you have 4 departments including ISP as follows-:

D1=>120 hosts

D2=> 120 hosts

D3=> 120 hosts

ISP=>5 hosts.

So how would you decide which IP address would be enough beforehand? ( English not my first language and I am unable to explain this properly).

Can I choose any IP address? Yes or No? If yes, is any IP address optimal i.e minimum address losses(I am explicitly designing for academia so no future expansion is assumed)?

What's the logic of choosing the optimum minimum loss IP address?

Say I choose 192.168.0.0/24 a class C ip address( Yes classes are obsolete but I am telling this in terms of network id and host id. It gives 8 bit host address so 256 hosts are possible.but there would be subnet and /## would keep on changing on VLSM.)

Say I choose 130.0.0.0/16 a class B ip address(in terms of hid and nid), what would happen?

How do I calculate that this is my needs, and this is the class of IP address or "this is the IP address" that I should choose? Or don't I need to calculate this at all? And subnetting is infinite host address possible?

I learnt VLSM from here

Relevant question

Zac67 says

For a private network, just use any subnet(s) from the RFC 1918 ranges 192.168.0.0/16, 172.16.0.0/12 and 10.0.0.0/8. There's no one-size-fits-all, but for most purposes, /24 subnets are the most reasonable.

He talks about classes being obsolute but doesn't answer how do you choose the optimum IP Address(for just now not thinking about future expansion). So please guide.

el_waleou
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1 Answers1

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I think I got my answer. (correct me if this software is faulty).

I will post the details image.

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So you just look at that subnet subnet mask=24

i.e 8 bits for hosts.

i.e total hosts possible is 256. But you count total hosts required ie 294 hosts hence this subnet mask is not allowed.

So can you choose 192.168.0.0/23. And that would let 512 hosts. I think this is correct answer. Correction very welcomed.

el_waleou
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