How to graph a mirror (span) port on a Cisco switch

Trying to graph traffic on mirrored ports of cisco switches.

Ports by design, when configured for monitoring, are up / down ( admin / operational )
and cisco is not going to change this.

GigabitEthernet1/0/11 is up, line protocol is down (monitoring)

I can easily graph these using MRTG -or- Cacti.

How do I graph these using Librenms?