How Many IPV4 Addresses Left?

As celegorm said, IP blocks (subnets) are allocated to organisations and therefore it's probable that you and your school have the same ISP and therefore have been given addresses from the same address space. Most schools/businesses would have bought static IP addresses, whereas your home one would be dynamic, and ordinarily these would come from different allocation pools within the ISP, but it depends how large the ISP is and how their infrastructure works - it doesn't really matter at the end of the day.
 
As celegorm said, IP blocks (subnets) are allocated to organisations and therefore it's probable that you and your school have the same ISP and therefore have been given addresses from the same address space. Most schools/businesses would have bought static IP addresses, whereas your home one would be dynamic, and ordinarily these would come from different allocation pools within the ISP, but it depends how large the ISP is and how their infrastructure works - it doesn't really matter at the end of the day.

Much better worded than my own response.

Also keep in mind, that within an ISP's subnet, they can subnet it themselves where for a basic example 147.1.x.x might be all of their static IP customers, where 147.2.x.x could be all of their dynamic IP customers.
 
Also keep in mind, that within an ISP's subnet, they can subnet it themselves where for a basic example 147.1.x.x might be all of their static IP customers, where 147.2.x.x could be all of their dynamic IP customers.
Yup, this is what I meant by different allocation pools within the ISP (that, and the possibility they may own more than one /8 subnet)
 
Right, I am still learning subnetting..

I posted a huge guide on subnet ting and super netting a few years ago.

I'll see if I can find it.

Regards businesses having more ip addresses than they need.
When I owned at the university of bath every workstation had a public address. 138.38.0.0/16 is their address space. There was surely no need for 65,000 public addresses assigned to a single entity...

Where I work now we have a few.blocks of addresses, mostly in /23 or /24 sized blocks...,
The thing is, whilst we do offer hosting. We probably have in the region of a thousand or more public addresses, and even though we don't use them, they are basically valuable by their scarcity, you're not just going to hand them to someone else saying oh well, we just don't use these anymore!
 
That was the guide I meant. Explaining how subnets work. I might clean that up a bit and stick it in the guide section. (Give me a few days!!)
 
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