I have had PRTG (free, thanks!) running on my home network (28 devices, 79 sensors) since October 2015, and it has been working very well.
Yesterday I was told that PRTG is accessing resources at work, across the SonicWall NetExtender Windows Client (version 8.6.256) -- SonicWall NetExtender is setup in the Probe Device -- and I note that SonicWall NetExtender is a Network Connection in the Windows Control Panel.
I don't see why/how PRTG is checking work resources across the VPN, because everything on my LAN is setup (per RFC 1918) with 192.168.1.x and the SonicWall NetExtender has its own 10.199.12.x address so completely different subnet.
Nothing in the "Dashboard Infrastructure Overview" nor review of all devices suggests that PRTG has any knowledge/insight about 10.199.12.x SonicWall NetExtender LAN range.
I have searched this PRTG Knowledgebase, and can not find anything about SonicWall NetExtender, that might explain packets being sent by PRTG across the SonicWall NetExtender (i.e. from my home LAN to work LAN).
But I did find the intriguing statement that "By default, on services startup, PRTG tries to detect all available network adapters on the system running a probe" and (as I mention above) the SonicWall NetExtender is considered to be a network adapter by Windows.
I spent a couple hours reviewing my PRTG configuration, and everything in my PRTG seems limited to 192.168.1.x