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CIDR (Classless Inter-Domain Routing) is a method for describing IP address ranges. Instead of using old "class" systems, CIDR uses a slash notation like /24 to indicate how many bits are used for the network portion of an address.
When you set up your home WiFi router, it creates a network like 192.168.1.0/24. This means:
/24 means the first 24 bits identify the networkUnderstanding your network helps with:
Subnetting allows you to divide large networks into smaller, more manageable segments. This improves security, reduces broadcast traffic, and enables better network organization.
VLSM allows you to use different subnet mask lengths within the same network. This maximizes IP address efficiency by allocating exactly the number of addresses needed for each subnet.
Also called "supernetting," this technique combines multiple networks into a single route advertisement, reducing routing table size and improving performance.
Large-scale network design requires careful planning of IP address space, considering future growth, routing efficiency, and administrative boundaries.
Internet routing relies heavily on CIDR aggregation to keep global routing tables manageable. ISPs aggregate customer routes to reduce the number of routes advertised globally.
With IPv4 address exhaustion, efficient subnetting and technologies like NAT (Network Address Translation) and CIDR have become critical for internet infrastructure.
Different routing protocols handle CIDR differently: