Labs

Tools give you an answer. Labs make you do the work. They are grouped by what you actually do in them: watch a mechanism run, build something and have it checked, or find out why something already broken is broken.

6 labs · free · no account Everything runs in your browser; nothing is saved or sent

Observe Watch it work

Run a mechanism a step at a time and read what each side actually sends. Nothing here touches a real network: these are models built to be paused, not packet captures.

1 lab

Transport TCP Three-Way Handshake Build every segment yourself: flags, sequence and acknowledgement numbers. Open a connection, send data, close it, and work out what a refused port or a lost segment does to both sides. Observe lab Start lab

Build Make it and get it checked

Design something, then have it marked. The check is the point: it names what is wrong and why, rather than showing you a score.

5 labs

Cable termination RJ-45 Wiring Game Drag the eight strands into the right pin order for T568A or T568B, then check your work. Straight-through and crossover, with the answer on request. Build lab Start lab Addressing Subnet Designer Size a block for every department from one base network. The lab checks capacity and alignment, then shows how much space your design wasted. Build lab Start lab Security Firewall Simulator Build an ordered rule-set and send a packet through it. Watch the top-down scan stop at the first match, then reorder and watch the verdict flip. Build lab Start lab Design Topology Builder Drop devices on a workspace and run cables between them. The check catches illegal links, devices over their port count, and anything stranded with no path back. Build lab Start lab Segmentation VLAN Playground Move hosts between VLANs and test any two of them. See why same-VLAN traffic just works, and what has to change before two VLANs can talk. Build lab Start lab

6 labs, and every one of them runs entirely in your browser. Nothing you build here is saved or sent anywhere: reload the page and you start with a clean workspace. Observe also gathers two tools, because they show the same kind of thing; they are marked as such above and are not counted as labs.

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