The scenario
Sales-PC (10.0.1.10/24), Eng-PC (10.0.2.10/24) and Shared-Printer (10.0.1.50/24) are all cabled to Office-Switch. The switch would happily carry frames between any of them. The problem is in the PCs' own settings: with a /24 mask, Sales-PC and the printer are on network 10.0.1.0/24, while Eng-PC is on 10.0.2.0/24. Each PC treats an address outside its own subnet as remote, looks for a router to send it to, finds no route, and gives up before sending anything.
What you will work out
Understand how an address and its mask define a subnet, and why two devices need the same subnet to talk without a router.
Why this matters
Subnets are how every network is divided, from office floors to cloud VPCs and container networks. A device given an address on the wrong subnet looks connected, with its cable in and its link light on, yet cannot reach its neighbours. Renumbering is one fix; in a real office you would more often keep departments on separate subnets on purpose and add a router between them, as the Router Between Two Networks lab shows.
Running it
Subnetting: Why /24 Matters opens on a canvas, already wired and addressed. Trace a packet through it hop by hop, or run the same topology live on real Linux network namespaces. How the two modes differ.
Open Subnetting: Why /24 Matters
Runs in your browser. No install, no signup, and the simulation starts instantly.
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