Subnet Calculator — IPv4 & IPv6 Articles

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Why a /16 Network with 65,534 Addresses Is Often the Wrong Design — Broadcast Domains, Segmentation, and VLSM

Why a /16 Network with 65,534 Addresses Is Often the Wrong Design — Broadcast Domains, Segmentation, and VLSM

A flat /16 network means every broadcast reaches all 65,534 devices and a compromised machine can reach every other device directly. Subnetting reduces broadcast domains and enables firewall policy enforcement at subnet boundaries. Here's why broadcast domain size determines network scalability, the trust-zone segmentation model (DMZ, application, database, management, users), VLSM for right-sizing allocations, and the RFC 1918 private address ranges.

Jun 21, 2026
Subnetting Math: Why /24 Gives 254 Hosts, How VLSM Works, and What the Slash Actually Means

Subnetting Math: Why /24 Gives 254 Hosts, How VLSM Works, and What the Slash Actually Means

A /24 gives 254 usable hosts, not 256 — because subnetting always reserves the first address (network) and last address (broadcast). Here's the 2^n−2 formula across all prefix lengths, VLSM (Variable Length Subnet Masking) for efficiently dividing address space into different-sized subnets, why route summarization (supernetting) is the reverse operation, and what the slash number in CIDR notation actually means in binary.

Jun 16, 2026
IPv6 Address Types: Why One Interface Has Link-Local, ULA, and Global Addresses All at Once

IPv6 Address Types: Why One Interface Has Link-Local, ULA, and Global Addresses All at Once

A single IPv6 interface normally has 3-4 different addresses simultaneously — link-local, unique local (ULA), and one or more global unicast addresses, each with different scope and purpose. Here's what each address type does, why ULAs exist alongside global addresses unlike IPv4's NAT model, and why privacy extensions cause global addresses to rotate.

Jun 12, 2026