How netmask works?

A netmask is a fundamental part of IP networking that defines which portion of an IP address refers to the network and which part refers to the host within that network. It does this by using a 32-bit number for IPv4 (or 128-bit for IPv6) that masks, or separates, the address into two sections: the network bits and the host bits. The network bits are represented by 1s, and the host bits by 0s. For example, in IPv4, a netmask of 255.255.255.0 (also written as /24) means the first 24 bits of the IP address are the network portion, while the remaining 8 bits are for host addresses. This allows devices to determine whether another IP address is on the same local network or if the traffic needs to be sent through a router. Essentially, the netmask acts like a filter, helping computers and routers efficiently route data by identifying networks and their boundaries.