Here is a hint in order to bond two interfaces together and then bridge the bond within Ubuntu
Firstly install the bond software
sudo apt-get install ifenslave sudo modprobe bonding
Now edit the /etc/network/interfaces. I set up the interfaces em1 and em2 into bond0 and then bridged.
Note: you can find the name of your interfaces with the command ‘ip link’
auto lo iface lo inet loopback auto bond0 iface bond0 inet manual bond-mode 1 bond-miimon 100 bond-slaves none auto em1 iface em1 inet manual bond-master bond0 auto em2 iface em2 inet manual bond-master bond0 auto br0 iface br0 inet static address 192.168.0.2 network 192.168.0.0 netmask 255.255.255.0 broadcast 192.168.0.255 gateway 192.168.0.254 dns-nameservers 192.168.0.220 192.168.0.221 192.168.0.222 dns-search sub.mydomain.se bridge_ports bond0 bridge_stp off bridge_fd 0 bridge_maxwait 0
After the configuration it’s easiest just to reboot, as stopping and reloading the networking didn’t work.