Short version: Will a Xen bridge work over a VirtualBox bridge? If so, how does it work?
Long version: I have Debian 6 (Squeeze) 64bit installed as a guest in VirtualBox, which is setup as a bridge connection using my local NIC in my laptop (not wireless).
Xen installs fine and I can start VMs. However, bridge networking on Xen does not work. DomU systems do not get an IP address, and even if the IP is set statically I can't ping DomU systems.
In Debian, I added the line (network-script 'network-bridge antispoof=yes') to /etc/xen/xend-config.sxp.
Creating a script /etc/xen/scripts/network-wrapper works with the following within it:
/etc/xen/scripts/network-bridge netdev=eth0 bridge=xenbr0 start
But if any changes are made to /etc/xen/xend-config.sxp and xend is started, then I will get the following error:
sigerr: command not found
It is possible to run Xen paravirtualization bridge from within VirtualBox. Just allow promiscuous mode in the virtual machine settings, and do not use a wireless NIC for the attached bridge adapter in VirtualBox. Here are my settings:
I tested both using Xen and a Debian bridge, they both work fine.
I know this is not convetional as stated by KCE, in the comment above, but it is a good setup for testing if you want to learn Xen, without having to use a seperate machine. So I hope this is of some help to someone else.