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Network Masks and Classfull Addressing

To better understand the scope of the IP addresses and the corresponding default (standard) masks, I will try to explain on Figure3.
These network masks are important in determining the Network Subnet Mask. This picture Figure3 is advisable to remember if you plan to work with the IT networks

Figure 3.

Default Subnet-mask or Network mask

In Figure3, we see what they look like the Default (standard) Network Mask for each class. This is called Classfull addressing.
Thus, for 'Class A' we see that the first Octet (byte) is written with the letter "N" meaning Network, and the other three bytes are written with the letter "H" which means Host.

To better understand, we will orient the binary records of network masks. The first 'Byte' tells us that a certain part of the network's IP address and it ranges from 0 to 126 and to see examples of on Figure3a. 

Also on Figure3a we can see that the first bit is always "0" (zero) [00000001 to 01111110]. So for a Class B we see that the first two bits are always "1" and "0" for the C class, we have the first three bits are always "1", "1" and "0" (see below Figure 3a)

In general, on Figure 3a. we see that for a particular network exchanged only Hosts bits (ie. bits that are located in bytes marked "H").
In our example, our the IP address 192.168.1.65 belongs to C class. Network unchanging part is 192.168.1. The last octet belong Hosts bits (our number 65) can be changed in the range: 1-254

Figure 3a.

 Public and Private IP Address Classes

Network: 192.168.1.0
IP address range of 192.168.1.1 - 192.168.1.254 (here belongs to our IP address 192.168.1.65)
Broadcast  IP Address: 192.168.1.255
Let's go to the next page tutorial.