Take a look at the Dude :-)
Some of it's features
- Auto network discovery and layout
- Discovers any type or brand of device
- Device, Link monitoring, and notifications
- Includes SVG icons for devices, and supports custom icons and backgrounds
- Easy installation and usage
- Allows you to draw your own maps and add custom devices
- Supports SNMP, ICMP, DNS and TCP monitoring for devices that support it
- Individual Link usage monitoring and graphs
- Direct access to remote control tools for device management
- Supports remote Dude server and local client
- Runs in Linux Wine environment, MacOS Darwine, and Windows
Unfortunately, I have not used it in years, and it has now become commercial, whereas it was free before.
You can enquire about the price or get the last free version from here.
Wait, that "last free version" is the same as the current download version, so I am not clear what it happening - maybe it's one of those which is free to use, but you can pay for support?