I have an RB1100 AHx4 that I run the dude on. It was working normally on 7.13 and prior versions, but after I upgraded RouterOS to v7.16 each of my networks under "Local-Network Map" discovers each and every IP in each network even for devices that don't exist. My Discovery mode is set to "reliable". Each one is discovered and shows the service "DNS". They all show an empty MAC address too. I have multiple RouterOS devices behind a Sonicwall router acting as the edge router.

This issue has been identified and will be fixed in the next release.

viewtopic.php?t=211157#p1099032

And:

SUP-165334 [7.16rc4] Unexpected dns (resolve) behavior

:resolve <name> server=<server> should bypass cache and send the query directly to server. Instead, version 7.16rc returns the value from cache.
A direct result of this is that The Dude will unexpectedly detect dns services on all hosts connected to the affected (7.16rc4) agent.

The issue has been reproduced, we look forward to fixing it on upcoming RouterOS versions.