Hello,
some sort of bug report. To whom it may be of interest :
No ping between host and guests ( but from and to any other node ).
Works when switching to a rtl8169 chip.
Details : Windows 7 pro 64bit host with intel nic driver 12.13.17.4 from 2015-06-18.
VirtualBox 5.0.4r102546 ( emulating 'intel pro/1000 mt desktop (8254oem)' ),
promiscuous mode for host and all guests.
CU - Stefan Schmohl