Guide on CIDR Notation

CIDR Notation stands for Classless Inter-Domain Routing, an IP addressing scheme that effectively replaced the older system known as Classful IP Addressing.

Importance:
CIDR allows for more efficient use of IP addresses and address space. It enables one IP address to designate many unique IP addresses. It is integral to IP routing, as it consolidates route information.

What is it:
CIDR is basically the combination of an IP address and its associated network prefix size. This is normally expressed as 'IP address slash prefix size', like 192.0.2.0/24. Here, '192.0.2.0' is the IP address and '24' denotes the size of the network prefix.

How it works:
With CIDR, an IP network is represented by a prefix. This is an IP address followed by a slash and the count of consecutive '1' bits in the network mask. For example, 192.0.2.0/24 is a CIDR block. The /24 after the IP address indicates that 24 of the 32 bits are the network part of the address, leaving the remaining bits (8 in this case) for specific host addresses.

Exam Tips: Answering Questions on CIDR Notation
Tip#1: Key terminology: Familiarize yourself with terms such as 'subnet mask', 'network address', 'broadcast address' and 'host addresses'.
Tip#2: CIDR Practice: Practice IP address calculation for CIDR notations. Websites like subnetting.net provide a practical ground for CIDR notation based calculations.
Tip#3: Subnetting: Understand the concept of subnetting and how CIDR allows us to divide IP addresses into subnets.
Tip#4: Relationship between subnet mask and prefix: To deduce the subnet from CIDR notation, subtract the prefix size from 32. That means /24 corresponds to a subnet mask of 255.255.255.0, as each octet in the mask is 8 bits. 32-24=8 bits left for host addressing.
Tip#5: Real-world scenarios: Master the application of CIDR in real world scenarios, solving problems based on it.