CCNA Labs: What is CIDR notation?

 The following video explains CIDR notation:

CIDR stands for Classless Inter-Domain Routing, which is a method of IP address allocation and routing used in modern IP networks. It is an alternative to the older classful network addressing scheme, which was based on classes of IP addresses that were assigned to networks of different sizes.

CIDR allows for more efficient use of IP address space by allowing network administrators to allocate addresses based on their specific needs, rather than being limited to pre-defined classful boundaries. It also simplifies the routing process by allowing for more flexible and granular route summarization.

CIDR notation is used to represent IP addresses and their associated network prefixes in a compact and standardized format. It consists of the IP address followed by a slash ("/") and a number that represents the number of bits used for the network prefix. For example, 192.168.0.0/24 represents the network with an IP address of 192.168.0.0 and a subnet mask of 255.255.255.0, which allows for up to 254 hosts on the network.

CIDR also introduced the concept of supernetting or aggregation, which allows multiple contiguous network prefixes to be summarized into a single, larger prefix. This simplifies the routing process by reducing the number of routes that need to be maintained in routing tables.

CIDR has become the standard method of IP address allocation and routing in modern IP networks, and is widely used in the Internet and in private networks. It is also a fundamental topic in many networking certifications, such as the Cisco Certified Network Associate (CCNA) and CompTIA Network+.