Understanding IP Addresses, Subnet Masks, and Subnetting (VLSM & CIDR)

IP addresses are logical identifiers used to locate devices on a network; they consist of 32 bits and are commonly expressed in dotted decimal notation such as 192.168.1.1.

The article shows how to convert between binary and decimal using the division‑by‑2 remainder method and the power‑of‑2 positional method, illustrating the conversion of the number 168 to binary (10101000).

IP addresses are divided into five classes (A‑E), with class A ranging from 1‑126, class B from 128‑191, and class C from 192‑223; the special addresses 0.0.0.0 and 127.0.0.1 are reserved for network and loopback purposes.

Subnet masks determine the network portion of an IP address; default masks are 255.0.0.0 (/8) for class A, 255.255.0.0 (/16) for class B, and 255.255.255.0 (/24) for class C, and they can be expressed in CIDR notation.

Private address ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are not routable on the public Internet and require NAT to access external networks.

Subnetting divides a network into smaller subnets; the article explains why subnetting is useful, lists benefits, and demonstrates calculations for the number of subnets (2^N) and usable host addresses (2^M‑2) after borrowing bits.

Variable Length Subnet Masking (VLSM) allows flexible allocation of subnet bits; examples show how a /24 network can be split into /27 subnets, adjusting the number of subnets and hosts per subnet.

CIDR aggregation (Classless Inter‑Domain Routing) combines multiple smaller networks into a larger prefix; the article contrasts VLSM (splitting) with CIDR (summarizing) and provides sample address blocks.