I’ve had this with certain kernels (2009.06) on opensolaris. Seems there is some incompatibility between some kernels and the opensolaris virtualbox network emulation. This only seems to effect linux virtual guests.
When you try to ping an address you get something like this…
[root@VA-DHCPWEB ~]# ping 192.168.9.15
PING 192.168.9.15 (192.168.9.15) 56(84) bytes of data.
64 bytes from 192.168.9.15: icmp_seq=1 ttl=128 time=1.85 ms
64 bytes from 192.168.9.15: icmp_seq=1 ttl=127 time=1.88 ms (DUP!)
I usually forward a port from my dsl router through to a VM, but it does not like it when the network is performing as above. I’m yet to find a permanent fix other than dropping back a kernel level.
I have no VLANs configured, and just have a single unmanaged switch on a single subnet. There is only a single nic configured on the virtual guest. Found this, but didn’t seem to resolve my issues. http://www.virtualbox.org/ticket/2713
If i ping the IP of the vm host it does not have the DUP packets, so it seems to be anything beyond the host adapter.
Update: This problem seemed to show itself with the new kernel / updates on the 2009.06 release of opensolaris. I’ve reverted back to 2008.11 and all seems to be working fine again. It may have something to do with project crossbow (new virtualization around the networking space) http://www.opensolaris.com/use/ProjectCrossbow.pdf