Subnet
Division of an IP network into smaller segments.
Subnetting is the process of dividing an IP network into smaller, logical sub-networks called subnets. This is achieved by borrowing bits from the host portion of an IP address and using them as part of the network identifier. The result is a subnet mask that defines the boundary between the network and host portions.
A subnet mask is a 32-bit value where network bits are set to 1 and host bits to 0. For example, the mask 255.255.255.0 corresponds to a /24 prefix (CIDR notation), which provides 256 addresses of which 254 are usable for hosts.
Variable Length Subnet Masking (VLSM) allows using different subnet masks within the same network for more flexible address usage. Subnet calculations are essential for network planning, firewall configuration and IP address assignment.
Key Points
- Divides networks into smaller segments for better control
- Subnet mask separates the network and host portions of the address
/24(255.255.255.0) is the most common mask in small networks- Network address and broadcast address are reserved in each subnet
- VLSM provides flexible subnet masks within the same network