Question 1

What is a subnet mask?

Accepted Answer

A subnet mask is a 32-bit number that divides an IP address into the network portion and the host portion. Bits set to 1 identify the network, bits set to 0 identify the host. For example, /24 (255.255.255.0) means the first 24 bits are network and the last 8 bits are host.

Question 2

What is CIDR notation?

Accepted Answer

CIDR (Classless Inter-Domain Routing) notation writes the IP address followed by a slash and a number 0-32 indicating how many bits form the network prefix. For example, 192.168.1.0/24 means a 24-bit network prefix with up to 256 addresses.

Question 3

What is the difference between network address, broadcast address and host range?

Accepted Answer

The network address is the first address of the subnet (host bits all zero). The broadcast address is the last address (host bits all one). The host range is the addresses in between, available for devices. The first and last are reserved.

Question 4

Does this calculator work for IPv6?

Accepted Answer

No, this is an IPv4-only subnet calculator. IPv6 has a 128-bit address space and uses similar but separate math. Use a dedicated IPv6 calculator for those addresses.