Problem with Network Bridging on Windows Server 2008

anthony.burns · Post by **anthony.burns** » 24. Oct 2008, 01:49

I'm attempting to set up a bridge between my host adapter and the tap adapter VirtualBox created. The host is connected directly to the Internet via the cable modem (no router). When I attempt to bridge the host adapter to the tap adapter, the bridge complains of not being able to obtain an IP address and my host adapter loses connection to the internet as well.

Post by **Sasquatch** » 24. Oct 2008, 21:44

This is because your internet Modem keeps a record of connected MAC addresses and will only provide an IP for the first MAC address it sees. If you power cycle your modem, it will clear that cache. When you create a bridge in Windows, it will generate a new MAC address just for the bridge. As opposed to Linux, which uses the first physical interface as it's MAC.

rab · Post by **rab** » 29. Oct 2008, 21:46

Sasquatch wrote:When you create a bridge in Windows, it will generate a new MAC address just for the bridge. As opposed to Linux, which uses the first physical interface as it's MAC.

So does that mean that packets from both the tap adapter and the host adapter will go out on the network with the bridge's mac address? Is there any way to have each source to the bridge send packets with distinct mac addresses?

Post by **Sasquatch** » 29. Oct 2008, 21:53

They already send packets with distinct MAC addresses, and that is the whole problem. The Guest uses the MAC shown in the settings, the Host uses the MAC address given to the Bridge interface, not the physical interface. Power Cycle your modem and only the first request will obtain an IP.

Since you only have one computer attached to the modem, why do you want to bridge it? You can use NAT for internet just fine. And if you want to be able to communicate to your Guest from the Host, read the manual about port forwarding, or just leave the virtual interface and remove the bridge. Put an IP address in the same range on both ends of the TAP adapter (Host and Guest) and you're done.

rab · Post by **rab** » 29. Oct 2008, 21:58

Sasquatch wrote:They already send packets with distinct MAC addresses, and that is the whole problem. The Guest uses the MAC shown in the settings, the Host uses the MAC address given to the Bridge interface, not the physical interface. Power Cycle your modem and only the first request will obtain an IP.

Since you only have one computer attached to the modem, why do you want to bridge it?

My problem is the opposite of the original poster's. I want both the guest and the host to use DHCP, but my DHCP server sees both requests as coming from the same mac address. I'm not using win2008 (XP in my case), and I see all packets from host and guest as having the bridge's mac address in the source field of the ethernet packets, as seen from the network. Is it possible the XP bridge is doing something like NAT but for ethernet?

yvonney · Post by **yvonney** » 31. Oct 2008, 07:23

with server 2008 host and a linux guest I'm able to use my computer wireless and VBox together to a bridge in server 2008 host of course.. much to my surprise no problems connecting.... and I have the bridge set to the gatwary of the router with a static ip address in the IP4 part of the bridge internet setting..

THING IS: I'm gonna have to report a bug or some incompatibility as I get a total blue screen after while ONLY when I'm running this way... as NAT all is fine...

best wishes everybody!!
hey, I heard that this could not be done with wireless being bridged to VBox guess..

thought?

Post by **Sasquatch** » 1. Nov 2008, 17:13

Yes, wireless and bridge doesn't always work. According to MS, it depends if the driver for your wireless supports promiscuous mode. This is something that is most of the time not supported. Some are having success with that, they are just lucky.

yvonney · Post by **yvonney** » 2. Nov 2008, 20:01

nice.. interesting. Thing is I've pondered that probably there a few ways to compensate, tweak etc. etc. as I do like the benefits of using the Host Interface feature....
I DO still get Linux Guest Freeze then a REBOOT once or twice a day though not like when I was using the network interface and bridging to my wireless card...

There's SO many variables I'll just enjoy and wait for what the updates may bring...

unless? hehehehe