The classful addressing system was the first major attempt to define a method for universal addressing of a large IP internetwork. There was a reasonable rationale for the system, as I mentioned in the overview of the classful scheme, and given that it was developed decades ago for a network that was limited in size, it did the job remarkably well for a long time.
No one ever expected the Internet to mushroom to anything close to its current size. As the Internet grew, the classful IP addressing mechanism showed some problems.
The three main problems with classful addressing are as follows:
Lack of Internal Address Flexibility Big organizations are assigned large, monolithic blocks of addresses that aren't a good ...