Something

suimui@nesthaekchen:~$ sudo ifup br0
Password:
/etc/network/interfaces:15: option with empty value
ifup: couldn't read interfaces file "/etc/network/interfaces"

auto lo
iface lo inet loopback
address 127.0.0.1
netmask 255.0.0.0

auto eth0
iface eth0 inet dhcp

auto eth1
iface eth1 inet dhcp

auto eth2
iface eth2 inet dhcp

ath0
iface ath0 inet dhcp

auto wlan0
iface wlan0 inet dhcp

auto br0
iface br0 inet dhcp
   bridge_ports eth0 ath0
   bridge_fd 5
   bridge_stp no
   pre-up ifup ath0