My final /etc/networking/interfaces file looks like (this is for Debian)
auto lo eth0 tap0 br0
iface lo inet loopback
iface br0 inet dhcp
bridge_ports eth0 tap0
bridge_maxwait 0
iface eth0 inet manual
iface tap0 inet manual
pre-up tunctl -b -u<my_user_name>-t tap0
pre-up ifconfig tap0 up
post-down tunctl -d tap0
I stole this from the following site joost.damad.be
Beware the username enttry above needs to be changed to your username… You will also need to install uml-utilities. Once I had this running I could start my image as follows:
qemu -net nic -net tap,ifname=tap0,script=no -hda debian.img