Network Notepad is a Windows application for building network diagrams. It is aimed at engineers who need to map and document infrastructure, rather than at producing illustrations for a slide deck.
Elements are placed by dragging and connected with labelled links, which is unremarkable until the diagram becomes something that can be acted on. Each device can carry configured actions, so a node in the drawing will open a session, issue a ping, or launch a browser against the address it represents, which turns a static topology into a working console. The freeware edition covers single page diagrams and the standard shape libraries, while the paid editions add multi page documents, linked diagrams that let one drawing drill into another, higher resolution export, and shared libraries for teams maintaining the same estate. The practical value is less in the drawing than in the fact that the drawing stays accurate, because a diagram people use to reach devices is a diagram somebody keeps current, whereas one that exists only for documentation drifts from reality within months of being finished.
It suits documenting an existing network better than designing a new one, and it is Windows only, which is the main constraint worth knowing before adopting it.
Link: networknotepad.com