Tonia,
Path Insight is licensed by interface on the devices monitored, so depending on how many interfaces you have on the devices you configure into Path Insight, that number will vary, as all network environments are different. Path Insight will attempt to monitor all interfaces seen on a device. It does allow the ability to ignore any interface so that the license utilized number comes down. Typically our customers will only monitor the interfaces that are active an supporting the voice environment, so that will bring that interface count down. As a basic estimate, I would say, take the number of phone endpoints and multiply by 3, but that is surely not an exact science.
Rick
