CIDR
CIDR is a notation that defines network prefix length (e.g., /24).
Updated: 2026-03-05
Definition
CIDR (Classless Inter-Domain Routing) represents the number of bits used for the network prefix in an IP address.
It enables flexible subnet sizes and efficient routing aggregation (supernetting).
Key points
- Prefix length defines subnet size
- Enables route summarization
- Replaced classful networking assumptions
Common mistakes
- Assuming /24 is always required (subnets can be any size).
- Confusing subnet mask and prefix length conversions.
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