I am asking fellow PRTG users to support this feature request please. The Paessler Development Team are willing to implement providing other customers like the expanded functionality described below.
On a router or switch, I would like to be able to see which interfaces are disconnected. This is very useful and PRTG does have the ability to show an interface as connected or disconnected, when the interface sensor 'Connection State Handling = Show alarm when disconnected'.
Unfortunately, it is not possible to do this without generating an alarm. To prevent an alarm for a down interface, it must configured to have a Connection State Handling = Ignore disconnected status, but this eliminates the link state from the PRTG user-interface. i.e. you cannot tell that an interface is disconnected.
The proposed setting 'Do not show alarm when disconnected' solves this need. I would recommend black or grey as the color to denote a port that is disconnected and has not generated an alarm.
The interface I am describing is 'allowed' to be down and should not require any ongoing administration in PRTG. The link state is informational and useful in researching events. E.g. Unused switch ports in a server room that come online at a later date; researching a server issue and looking to see if there was a link loss; user computer connections that are down if they power off. Note: The suggested functionality should not be confused with a down 'acknowledged' alarm, as this requires manual intervention and a persistent alarm states.
Furthermore, creating sensors for unused (down) interfaces does not have to be driven by a reoccurring auto-discover of the device. Simply creating sensors for all up and down interface during the initial auto-discover and defaulting to the proposed setting 'Do not show alarm when disconnected' solves this need. This also eliminates the need to add and delete sensors as ports are assigned and unassigned to servers.
Let me know what you think. Thank you for your consideration on this.