What does CIDR notation mean, and what does /24 signify?

• A. CIDR indicates the total number of subnets; /24 means 24 subnets.
• B. CIDR indicates the network prefix length; /24 means the first 24 bits are network, leaving 8 bits for hosts.
• C. CIDR indicates the broadcast address; /24 sets the broadcast to 255.255.255.0.
• D. CIDR indicates the protocol used to route; /24 is not a valid value.

Answer: (B)

CIDR notation shows how many of the address’s leading bits form the network portion. For IPv4, a /24 means the first 24 bits are fixed as the network, and the remaining 8 bits are available for host addresses within that subnet. That corresponds to the subnet mask 255.255.255.0, so addresses sharing the same first 24 bits belong to the same subnet. In this setup, you have up to 256 total addresses in the subnet (often 254 usable hosts after excluding the network and broadcast addresses). The other interpretations—such as indicating the total number of subnets, setting the broadcast address, or describing a protocol—don’t describe what CIDR does; CIDR is about the length of the network prefix.