Strange network bridge behaviour

[mintochris]

After upgrading to hardy (tested on a clean install as well though) my network bridge setup was behaving very oddly, my /etc/network/interfaces was;

/etc/network/interfaces

auto lo
iface lo inet loopback
iface br0 inet dhcp
bridge_ports eth0 eth1
auto br0

In gutsy this (along with a single sudo ifup br0 after setup) was enough.
In hardy this meant that neither network card worked, I couldn't ping the router or reach the web.

I could fix it if i brought the network bridge down with

sudo ifdown br0

and raised it again with

sudo ifup br0

but ONLY if i accessed the internet BEFORE i issued the second command.

Eventually I tracked the problem down to a duplicated IP assigned to both br0 and eth1, so... finally, the important bit.

In hardy to get the network bridge working you must change /etc/network/interfaces to the following; (where eth* is your NIC that is connected to the internet)

/etc/network/interfaces

auto lo
iface lo inet loopback

iface eth* inet manual
up ifconfig $IFACE 0.0.0.0 up
down ifconfig $IFACE down


iface br0 inet dhcp
bridge_ports eth0 eth1
auto br0

and then reboot and type the following into the terminal

sudo ifup br0

then it should work, at least until the next update.
hope this helps someone, as it took me ages to work out!