The webpage you reference says
Not every network environment requires subnets.
In theory that may be true, or may not even be true in theory. Like if you have two computers connected with a cable, and no router, no switch, no layer 3 addressing scheme. Then pick one computer, is that on a physical subnetwork.. maybe, maybe not.
According to wikipedia
"A subnetwork, or subnet, is a logical, visible subdivision of an IP network."
I have my doubts even wikipedia is correct e.g. as if subnetworks can't be physical or that it's only limiting itself to IP, but the webpage you quote from is using a definition like that. And clearly if you are given a subdivision of the internet(a rather famous IP network), or even just given an IP of a subnet given to your ISP, then your network has / is on a subnet.
Even the network it describes has the subnet it has been given.
So the webpage you refer to is just plain wrong!
What this webpage means is that not every network environment requires further subnetting. I could agree with that
I guess another definition of subnet might say that the IP address block given by IANA is just called that, an IP address block, and not a subnet. I guess you may then say there is no subnet.. Though even then there is really 'cos you'd have a subnet mask. Ultimately, terms need to be defined.
For example, if your organization’s network has 254 or fewer hosts — and the network lives in one building (what a concept), there’s no reason to subnet it.
The webpage means no reason to subnet it further (i.e. no reason to subnet the subnet it has been given).
And even that is not true. And 254 hosts or not is absolutely irrelevant. An administrator may want to separate things, and have a subnet for one group in the building, and a subnet for another group in the same building, and a firewall in between.
And if hosts were in different buildings, I suppose there would likely be different subnets, but maybe it's possible to have them on the same subnet, there probably are many ways, i'm not sure if they are all viable ways, but either way, it looks like the webpage is wrong there too.
The title of the page says
Need More Addresses? Try Subnetting and NAT (TCP/IP) Part 1
By definition, subnetting is not going to get you more addresses. It's like if you have x number of people and they get into groups, then however they group up it's still the same number of people.
NAT will get you more addresses because it involves you using an additional subnet, one that you weren't using previously.
in what circumstances would each host need a globally allocated
address and not use NAT?
Multiple servers online is the typical reason. And a company that has been given the IP addresses.
Though even there NAT could be used in theory. But I think NAT devices port forwarding tend not to be used there as it's unnecessary extra work, even if there were a super professional NAT device that makes port forwarding very professional, techie and administrable from the command line, it's possible. But if you're asking When people use multiple public IPs it's for the multiple servers. But I am not sure that it'd be a 'need' as in theory it could be done from behind NAT.
Remember that the public IP Addresses came first.. before NAT. So it's more of a question of Why one needs NAT (and that question has a clear definite answer which brought about the invention of NAT). Now as a SOHO person you're seeing all these private ip addressese and asking why you need all the public ip addresses! and yeah technically I suppose you don't need more than one! but you might like more than one so as to not do lots of port forwarding on the GUI of a NAT device.
if you've got an IP address range which lets you have more than 254
hosts, why not just keep assigning IP addresses to each host?
254 is irrelevant.
You can subnet I guess if it's really big you might have a speed issue with You can google about subnetting increasing performance.
The answers on this question expands on that
One answer suggests that even a /22 is fine (that's 2046 hosts).
And another answer says if properly configured then even a large subnet isn't a problem. (but to configure it "properly" may require a lot of expertise and familiarity with the issues!). One issue is too many broadcasts.. but there are others issues mentioned there that could affect performance. And some devices maybe aren't really designed/tested with a very large number of hosts in mind.