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What is Subnetmask?

In ipv4 Subnet Mask define that how many bits are acting as network bits and how many bits are acting as host bits.

Default Subnet Mask of classes :

Class

Subnet Mask

Formula

A 255.0.0.0 /8
B 255.255.0.0 /16
C 255.255.255.0 /24

What is Classfull IP Addressing :-

When default Subnet Mask is used in configuring the IP address, then it is known as classful IP addressing.

What is Classless IP Addressing :-

When we change the default Subnet Mask and configuring the IP address, then it is known as classless IP addressing.

Class Range Subnet Mask Formula NID (Total) NID (Available) HID Use
A 0-127 255.0.0.0 N.H.H.H 8 7 24 Uni/Broad Casting
B 128-191 255.255.0.0 N.N.H.H 16 14 16 Uni/Broad Casting
C 192-223 255.255.255.0 N.N.N.H 24 21 8 Uni/Broad Casting
D 224-239 N/A N/A N/A N/A N/A Multi Casting
E 240-255 N/A N/A N/A N/A N/A Research &

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