Bridged networking not working anymore

[ecejjar]

VirtualBox 5.0.8 (before 4.3.10)
Host: Ubuntu 14.04 x86_64 (kernel 3.13.0-66-generic)
Guest: Ubuntu 14.04 x86_64

I have a problem with bridged networking. Up to two days ago everything went fine with my VBox 4.3.10. I am running one Ubuntu 14.04 x86_64 guest with two virtual NICs. The first NIC is using NAT and works like a charm. The second NIC is using Bridged Adapter to a local host bridge (i.e. a bridge not connected to any physical NIC in the host). I use this second NIC to ssh from the host into the VM at a fixed IP address.

Now the second virtual NIC does not work anymore. When the VM boots up VBox should add the host side of the virtual NIC to the host bridge, but when I check the host's local bridge status I see this:

Code: Select all

sudo brctl show br0
bridge name	bridge id		        STP enabled	interfaces
br0		        8000.000000000000	no		

Inside the guest I see the virtual interface as eth1, but it is unusable since it is not connected to anything in the host.

I have changed the second virtual NIC to NAT mode and it works fine. I have also upgraded to VBox 5.0.8 but the issue with bridged networking remains.

Any clues on where should I look into to diagnose the problem?

Thanks in advance!

[Perryg]

Post the guests log file ( as an attachment ). Right click on the guest in the Main Manager then click show log. Save and post as an attachment. Compress if it is too large to post.

Other questions will follow once I see the log file.

[ecejjar]

Here it goes.

I've been doing some research on my own. It happens that if I go back to a previous snapshot of my guest, when it comes up the bridged interface is working. However, after a while the guest's interface "loses" its IP address. Going deeper into the problem, I see that the guest times out trying to get a DHCP answer for the interface (see the attached screenshot).

I did a packet capture on the bridged interface in the host. I can see the DHCP requests from the guest, but no answer ever comes from dnsmasq in the host. Strangely, when the guest comes up right after going back to a previous snapshot dnsmasq in the host leases an address to the guest, but stops doing it after a while.

Thanks!