Created attachment 154247 [details] tcpdump for Linux guest * Using Port versions virtualbox-ose-4.3.24 / virtualbox-ose-kmod-4.3.24 * I use Host-Only for all guests. Network vboxnet0 has DHCP enabled, but some guests use static-IP/static gateway as defined from within the guest's config. * Subnet on vboxnet0 is /28 (broadcast 192.168.56.15). There's no guest running on 192.168.56.1 which is the gateway/DHCP * I have 3 general classes of guests: *BSD, Windows, Linux and 3 different things happen re networking when I start these guests. * Linux guests: cannot ping gateway (192.168.56.1), cannot ping other guests, can ping itself. netstat shows correct route table. * Windows guests: Same problem as Linux, netstat shows correct route table. Then I start a *BSD guest and can now can ping Linux guests, gateway and outside of subnet. However, network status does not behave in a consistent manner. * BSD Guests: Behave as expected, can ping other guests, gateway and outside of subnet without problems. * Guests of the other 2 OS categories appear to behave more sanely (conjecture) if a BSD guest is started first, before the other guests. The BSD guest does not need to keep running. A simple start/stop is sufficient to activate the vboxnt0 network path. * tcpdump on vboxnet0 shows exactly what I have described: No traffic reaches vboxnet0 from Linux/Windows guests. After a BSD guest is started then stopped, pinging from the Linux guest shows that traffic reaches vboxnet0, and that it gets no response: 19:24:05.531541 ARP, Request who-has 192.168.56.1 tell 192.168.56.13, length 46 19:24:05.531547 ARP, Request who-has 192.168.56.1 tell 192.168.56.13, length 46 * Full tcpdump for startup/shutdown process of the Linux guest is attached.