Why doesn't eth0 get an ip address when set up in a bridge?

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http://unix.stackexchange.com – I'm trying to understand how dhcp for IPv4 is used with bridging. eth0 is configured to be in br0. This is working just fine but only br0 gets a dhcp lease, while eth0 doesn't. Both are configured with BOOTPROTO=dhcp. If anything, I would have expected eth0 to have the IP address and br0 as a "layer 2 device" to have none, not the other way around. Any suggestion would be greatly appreciated. (HowTos)