1. I use two nics per box. One is the hardware/host NIC, the other my VM bridge/tap interface.
2. Remember to set the hardware interface (eth0/eth$X) to promiscuous on the VM interface.
3. Create a tap interface using tunctl. A very handy feature of tunctl is the ability to set user and group so your VM's can run under lower privileges. In Debian, I find the package with 'apt-cache search tunctl' and it returns the right name.
Create a bridge using brctl. In Debian, I believe the package is called bridge-utils. Setup varies depending on the package you use. The tap interface is one end, the bridge interface is the other. then the BRIDGE gets assigned an IP address. I set it all in /etc/network/interfaces.
Your ifconfig-fu will be much better after setting a couple of VM's up!
Last edited by mpapet; 07-16-2012 at 05:40 PM.