What does CIDR notation signify and what does a subnet mask indicate?

What does CIDR notation signify and what does a subnet mask indicate?

• A. CIDR expresses IP address blocks (e.g., 192.168.0.0/24); a subnet mask defines which portion is network vs host bits.
• B. CIDR is a type of router; subnet mask is a tool for encryption.
• C. CIDR is used for domain name resolution; subnet mask is used for routing.
• D. CIDR indicates DNS zone; subnet mask defines the IP address range.

Answer: (A)

CIDR notation expresses how large a block of IP addresses is by showing how many bits at the start of the address are fixed as the network portion. The “/n” after an IP (like 192.168.0.0/24) means the first n bits are the network, and the remaining bits define hosts within that network. In the example, the first 24 bits are the network, leaving 8 bits for host addresses, which yields up to 256 addresses in that block (with two unusable for network and broadcast). A subnet mask does the same job in dotted-decimal form. It marks which bits are used for the network (1s) and which are for hosts (0s). For instance, 255.255.255.0 corresponds to /24, indicating the first 24 bits are the network portion. Routers use this mask to determine whether a destination is on the same local network or should be routed elsewhere, and you derive the network address by ANDing the IP with the mask. In short, CIDR shows the size of the block, and the subnet mask defines which bits partition the address into network and host parts.

CIDR notation expresses how large a block of IP addresses is by showing how many bits at the start of the address are fixed as the network portion. The “/n” after an IP (like 192.168.0.0/24) means the first n bits are the network, and the remaining bits define hosts within that network. In the example, the first 24 bits are the network, leaving 8 bits for host addresses, which yields up to 256 addresses in that block (with two unusable for network and broadcast).

A subnet mask does the same job in dotted-decimal form. It marks which bits are used for the network (1s) and which are for hosts (0s). For instance, 255.255.255.0 corresponds to /24, indicating the first 24 bits are the network portion. Routers use this mask to determine whether a destination is on the same local network or should be routed elsewhere, and you derive the network address by ANDing the IP with the mask. In short, CIDR shows the size of the block, and the subnet mask defines which bits partition the address into network and host parts.