Networking TCP/IP Math

Example 9

Find the class of the address:           227.12.14.87

Solution

The first byte is 227 (between 224 and 239); the class is D.

Example 10

Find the class of the address:          193.14.56.22

Solution

The first byte is 193 (between 192 and 223); the class is C.

Example 11

In Example 6 we showed that class A has 2³¹ (2,147,483,648) addresses. How can we prove this same fact using dotted-decimal notation?

Solution

The addresses in class A range from 0.0.0.0 to 127.255.255.255. We notice that we are

dealing with base 256 numbers here.

Each byte in the notation has a weight.

The weights are as follows:

256³ , 256², 256¹, 256⁰

Last address:  127 ´ 256³ + 255 ´ 256² +
255 ´ 256¹ + 255 ´ 256⁰ = 2,147,483,647

First address:    =   0

If we subtract the first from the last and add 1, we get 2,147,483,648.