I'm running VirtualBox 4.1.8 on Ubuntu 64-bit, which is connected to the the network via wireless adapter WLAN0.

I'm running another Ubuntu as a VM on VirtualBox with "Bridged Adapter" via WLAN0, and it has some network problems:
1) ping results in "(DUP!)" messages as seen below
2) the Ubuntu guest does get a public IPv6 address from the modem, but IPv6 doesn't work

When I switch the host system to fixed ethernet and disable wifi, the problem is gone: ping works normal, IPv6 works.

Problem seems related to https://forums.virtualbox.org/viewtopic.php?f=7&t=45886 which has no solution.

Any tips?


Code:
sander@sander-VirtualBox:~$ ping ping.xs4all.nl
PING uucp1.xs4all.nl (194.109.21.51) 56(84) bytes of data.
64 bytes from uucp1.xs4all.nl (194.109.21.51): icmp_req=1 ttl=59 time=22.8 ms
64 bytes from uucp1.xs4all.nl (194.109.21.51): icmp_req=1 ttl=58 time=23.0 ms (DUP!)
64 bytes from uucp1.xs4all.nl (194.109.21.51): icmp_req=2 ttl=59 time=20.2 ms
64 bytes from uucp1.xs4all.nl (194.109.21.51): icmp_req=2 ttl=58 time=20.3 ms (DUP!)
^C
--- uucp1.xs4all.nl ping statistics ---
2 packets transmitted, 2 received, +2 duplicates, 0% packet loss, time 1002ms
rtt min/avg/max/mdev = 20.254/21.612/23.022/1.342 ms
sander@sander-VirtualBox:~$ ping 192.168.1.254
PING 192.168.1.254 (192.168.1.254) 56(84) bytes of data.
64 bytes from 192.168.1.254: icmp_req=1 ttl=64 time=15.9 ms
64 bytes from 192.168.1.254: icmp_req=1 ttl=63 time=16.0 ms (DUP!)
64 bytes from 192.168.1.254: icmp_req=2 ttl=64 time=5.10 ms
64 bytes from 192.168.1.254: icmp_req=2 ttl=63 time=5.27 ms (DUP!)
^C
--- 192.168.1.254 ping statistics ---
2 packets transmitted, 2 received, +2 duplicates, 0% packet loss, time 1006ms
rtt min/avg/max/mdev = 5.105/10.578/16.027/5.391 ms
sander@sander-VirtualBox:~$