The diagramming program for everything. Open Source.

Features I love:

• Files can be saved not only in drawio XML format, but also as .png, .svg and html - all without loosing meta information. Note: I recommend attaching .drawio to the filename to make the actual file type obvious, e.g. Networkdiagram.drawio.png.
• Available as a Browser Application as well as a offline useable Desktop Application (available through automatic and awesome github releases).
• Object Anchors
• Ease-of-Use

The shapes I use for Network Diagrams are:

• Network / Cloud & Enterprise (for Server)
• Network / Cisco19 (for Network Components)
• Network / Veeam (for Backup-things)

It was all really intuitive and head-on start.

I recommend and show it to literally everyone. There is no exception.