(4) Calculating IPv4 Subnets and Hosts - CompTIA Network+ N10-009 - 1.7

Variable-Length Subnet Masks (VLSM)

A method that allows network administrators to define their own masks for subnets of varying sizes, optimizing IP address allocation.

Subnet Mask

A 32-bit number that divides an IP address into network and host portions.

Class A Address

An IP address from the range 1.0.0.0 to 126.255.255.255, usually with a default subnet mask of 255.0.0.0.

CIDR Block Notation

A compact representation of an IP address and its associated network mask, e.g., /24.

Powers of 2

A mathematical basis for calculating the number of subnets and hosts, using powers of two.

Number of Subnets

Calculated as 2 to the number of subnet bits.

Number of Hosts

Calculated as 2 to the number of host bits minus 2 to account for the network and broadcast addresses.

Host Bits

Bits reserved in an IP address for identifying host devices within a subnet.

Subnet Bits

Bits in an IP address that are used to create multiple subnets from a single larger network.

Broadcast Address

A special address that allows information to be sent to all hosts in a subnet.

Default Gateway

The device that routes traffic from a local network to other networks, such as the internet.

192.168.11.0/26

A Class C IP address, where the default bits are 24 with 2 subnet bits, allowing for 4 subnets of 62 hosts each.

172.16.55.0/21

A Class B IP address that has 21 network bits and supports 32 subnets with 2,046 hosts each.