Network bridge does not work with multiple mac addresses on the guest side

[Ivo Smits]

The Bridged network mode seems to be unable to deal with multiple MAC addresses being used to send packets from a guest. This situation occurs when a network bridge is configured inside a guest system.

It looks like the virtualbox network bridge can only keep track of one MAC address for which it accepts incoming packets for the guest; that mac address is most likely set to the source address of the last outgoing packet from the guest. This results in major packetloss for both the guest and systems on the other side of the guest's network bridge.

In most cases, the described behaviour is close to how a normal NIC would behave. However, if the NIC is in Promiscuous mode (which is the case for network bridges), the NIC should present all packets it receives to the guest, without filtering.

It may not be feasible to present all received packets to the guest for performance reasons; however if the guest explicitly enables promiscuous mode it is requesting to receive all such packets, and usually needs this behaviour.

A reasonable alternative to accepting *all* packets would be to enlarge the MAC address buffer, but this would require a far more complex network switch implementation.

[Aleksey Ilyushin]

Did you use e1000? Can you try if it works with pcnet adapter?

[peter.debruyne]

I had a similar issue with Virtualbox 4.0.4 and the e1000 adapter. After changing the vm to use the pcnet III adapter, multiple mac addresses active inside the guest (promiscuous mode) worked fine and were reachable from outside the vm.