Dictionary · Networking Fundamentals
CIDR
CIDR — Classless Inter-Domain Routing
Addressing · Intermediate
A way to write a network prefix with a slash and the number of network bits, such as /24. It replaced rigid class A, B, and C boundaries.
Instead of assuming an address class, you state the prefix length directly. A /24 has 256 addresses in the block, while a /30 has only four.
Picture it
In 10.1.8.0/24, 24 is the number of network bits, not the number of hosts. The block contains 256 addresses.
Example: 10.1.8.0/24 means the first 24 bits identify the network. The older classful name is unnecessary.
Common misconception
- The number after the slash is not the number of hosts. It is the number of prefix bits.