vde_switch bridge question?

[Ishwar Rattan <ishwar@pali.cps.cmich.edu>]

I have a debian based Linux box (ProMepis) running a iptables
firewall on interface eth0. I want to try bridging for qemu based
hosts. Using vde_switch software I set up a bridge (br0) to which
intefaces eth0 and tun0 are bridged to it.

1. I assume that now the firewall should be run on interface br0?
   If I do that I can connect to dept LAN after setting up the bridge
   else not.

2. How to use tun0 interface in the guest OS? Is the interface
   assigned an ip-address before starting the the guest OS?

Any pointers will be appreciated.
-ishwar