What constitutes being "connected"?
Years ago in the days of analog telephones, being connected was clearly understood; you literally had a completed electrical circuit between the endpoints. But on a packet switched network, the terms "connected" and "active" are dubious.
Consider ARP. All arp tells you is if traffic from/to a device has been seen "lately", which might be as little as 10 minutes ago. Once clients go "quiet", the arp entries will disappear until activity resumes. Yet, the client may still be "connected", as in their laptop is connected over ethernet or wireless, they have an active DHCP lease and IP assignment, etc.
Given the above, and depending on what YOU mean by connected, it might make more sense to actually ping around the network, just in case some devices have gone silent, if only temporarily.
That's why when routers attempt to create any sort of connected/active list of devices, you have to take it w/ a heavy grain of salt. By design, packet switched networks strive to be stateless, which is what makes them so powerful and flexible. But it also makes it that much more difficult to define what exactly is a connected/active device. And not everyone will agree w/ the definition.
