try this.
Get the port id by hovering over each port and looking for port=[number] in the URL at the bottom of the browser. Alternately you can click into the port and it will show in the address bar.
Go here - https://[your librenms URL]/graphs/id=[comma separated list of ports you want to graph]/type=multiport_bits
Right click the image and select “Copy Image Location”
Add the widget “External Images” to the dashboard
Paste the link you copied above in to the “Image URL” box, and delete everything before “graph”. The result should look like this:
graph.php?id=1217%2C1218&type=multiport_bits&from=1480621200&to=1480707600&height=317.66666666667&width=1664.1
Change the from= and to= values in the URL to the date range you want to display. For instance, “from-1d&to-300” will display from one day ago to five minutes ago.
In order to make the text scale with the size of the widget window append, “&absolute=1” to the end of the URL.
If you want clicking the image to result in a larger image opening, paste that into the, “Target URL” box. I adjusted my from/to so that it would open to a seven day view.