Here is That email which written and applied in 1996
In 1996 the guys over at The Internet Engineering Task Force (IETF) had to decide what range of IPv4 addresses they could give away for internal use, meaning that these IP addresses would be assigned only to devices in closed networks and would not be available on the public internet.
Why would they do that exactly? The main reason is a limited number of IP addresses. 4,294,967,296 to be exact. If all internet-enabled devices would have their own unique IP address we would have ran out of them a long time ago.
Together with the(IANA), they have reserved three “blocks” of the IP address space for private networks:
- 10.0.0.0 – 10.255.255.255 (Class A)
- 172.16.00 – 172.31.255.255 (Class B)
- 192.168.0.0 – 192.168.255.255 (Class C)
Depending on how large your network is, you would choose from one of these network classes. Class A gives you 16,777,216 IP addresses, Class B – 1,048,576 and class C 65,536.
Since we are talking about private home networks, I don’t think you would even come close to connecting 50 different devices at the same time to one router. And, the smaller the network, the less problems it will cause.
For this reason, most Broadband routers have an even smaller range of IP addresses: 192.168.0.0 to 192.168.0.255. This means that you can connect up to 254 devices to your network (254 + 1 router). That should be enough for most people.
But what if 255 IP addresses aren’t enough?
There is really nothing stopping you from using a Class A or B network. They are made for private use and anybody can create one (at least with some technical skills).
Class A networks are great for large businesses with lots of connected devices. Having a 10.x.x.x network allows you to structure and maintain a good overview over all the devices connected to the private internet.
Let’s say you own two buildings and each is 254 stories high (because who doesn’t?). And on every floor there are around 250 different computers.
What you could do now is to create a neat IP address structure for your business. For instance, a computer on the 120th floor of your first building would be 10.1.120.x, and a computer on the 223rd floor of your second building would be 10.2.223.x. Get it?
Long story short, we are using 192.168.X.X IP addresses because this is best practice. The IETF has created three IP ranges for private networks, with Class C being the smallest and easiest to control and maintain. This is why most routers use exactly this IP range.
However, you are free to use any of the three network classes depending on your private and/or business needs.
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