computers networks tutorials

The IPs which cannot be configured in a device :

Case-1 (All network bits cannot be zero) :

Class

Formula

A 0.H.H.H
B 0.0.H.H
C 0.0.0.H

Case-2 (All host bits cannot be zero) :

Class

Formula

A N.0.0.0
B N.N.0.0
C N.N.N.0

Case-3 (Broadcast IPs) :

Class

Formula

A N.255.255.255
B N.N.255.255
C N.N.N.255

Case-4 Class D (Multicasting IPs)

Case-5 Class E (Reserved for research & Development)

What is CIDR ?

CIDR stands for Classless Inter-Domain Routing. It is the method which involves taking host bits and converting them into network bits. It is used in subnetting to reduce the wastage of IPs.