Comment 2 for bug 260353

This is increasingly important also if you use VirtualBox with host network configuration (almost all installations do that). It's quite painful to get this right w/ NM and VirtualBox. Here's my /etc/network/interfaces file:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual
        up ip link set $IFACE promisc on
        down ip link set $IFACE promisc off

auto tap0
iface tap0 inet manual
        up ip addr add 0.0.0.0 dev $IFACE
        down ip addr add 0.0.0.0 dev $IFACE
        tunctl_user matteo

auto br0
iface br0 inet manual
        up brctl stp $IFACE off
        up ip addr add 192.168.1.15/24 dev $IFACE
        up ip route add default via 192.168.1.1 dev $IFACE
        down ip route del default via 192.168.1.1 dev $IFACE
        down ip addr del 192.168.1.15/24 dev $IFACE
        down brctl stp $IFACE on
        bridge_ports all tap0

I'd consider this a bug rather than a wishlist: if a bridged interface exists and some ethernet cards are part of it, it's the bridge that should be used with DHCP/static address, not the ethernet cards.

Problem is, br0 and eth0 have the same MAC address, so you can't force NM to use one address instead of the other for configuration of the wired connection.

There should be another way to prioritize interfaces, or better always preferring bridges above ethernet cards when looking for a certain MAC address to set up the connection. This should be doable.

Sorry if I'm wrong. I'm just learning about bridging in GNU/Linux, so I may have made some wrong assumptions.