Can you explain what the term CIDR means and what it is used for in the networking industry?

CIDR (Classless Inter-Domain Routing) is a method of representing and allocating IP addresses and routes in a network, which replaced the outdated class-based system of IP addresses.

Instead of fixed classes (A, B, C), CIDR uses prefix notation, for example: 192.168.1.0/24, where the number after the slash indicates the number of bits that define the network.

This allows for more flexible and efficient allocation of address spaces, reducing the number of unused IP addresses and simplifying routing.

Example:

• 10.0.0.0/8 — a network with 16 million addresses
• 10.0.0.0/16 — a subnet within the previous with 65 thousand addresses

CIDR is widely used in network configurations, routers, and in organizing internet routing.