Computer networking, series 1

I’m forced to brush up on computer networking because I took courage to set up an email server for my compadre’s client.

As I was doing so, may realizations came. Like on the IP address ranges. I came to know that for Class A addresses ( through, the first octet (first of four numbers separated by a dot) is the network number, enabling per site to have 1.6 million hosts/machines. For Class B ( through, the network number is the first two octets, allowing 16,320 networks to have 65,024 hosts each. For Class C ( through, the network number is the first three octets, allowing nearly 2 million networks to have 254 hosts each. Classes D, E and F ( to, I understand are used for special purposes only. I wonder why, though. Or, I don’t give a damn.

So the lower the class, the higher number of octets serving as network number. Is it the reason why small networks opt for Class C? With Class C range, there is only one host number, which makes it easy to administer.

I also wondered first whether unique IP addresses already ran out as, for sure, there are much more than three million computers already connected to the world. Now, I see that the issue of unique IP concerns the Internet Service Providers, whose IP addresses are assigned by a central authority called Network Information Center.

I also learned that there are IP address ranges that are reserved for private use or network. Can I also call this “internal network”? These are:

Class Networks
A through
B through
C through

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