Subnettmasken

Subnettmasken, or subnet mask in English, is a fundamental concept in computer networking, specifically within the Internet Protocol (IP) addressing system. Its primary function is to divide an IP address into two parts: a network address and a host address. This division is crucial for efficient routing and management of network traffic.

An IP address, such as a version 4 address, is a 32-bit number typically represented in dotted-decimal notation (e.g., 192.168.1.1). A subnet mask is also a 32-bit number, expressed in the same format. The mask uses a series of ones followed by zeros to delineate the network and host portions. All bits in the subnet mask that are set to one correspond to the network portion of the IP address, while the bits set to zero represent the host portion.

By using a subnet mask, devices on a network can quickly determine whether another IP address is on the same local network or if it resides on a different network, requiring a router to forward the data. This process is known as subnetting. Subnetting allows administrators to break down a large network into smaller, more manageable subnetworks. This not only improves performance by reducing broadcast traffic but also enhances security by isolating different segments of the network. The choice of subnet mask directly influences the number of available IP addresses for hosts within a given network or subnet.