interface_traffic probe.
interface_traffic probe offers a probe callback named "get_total_interface_count" which give you number of monitored interfaces.
How to run the callback from Infrastructure Manager.
Highlight interface_traffic probe, CTRL+P, then Probe Utility dialog is opening.
Select "get_total_interface_count" in the Probe commandset dropdown, then press green (execute) button.
How to run the callback from command line.
> cd <UIM Install Path>\bin
> pu -u <UIM user> -p <password> /<domain>/<hub>/<robot>/interface_traffic get_total_interface_count