http://backreference.org/2010/07/28/linux-bridge-mac-addresses-and-dynamic-ports/
There are two ways to set the MAC address of an interface. The old way is using ifconfig:
# 00:0a:e7:2c:44:2a is eth0's MAC address
# ifconfig br0 hw ether 00:0a:e7:2c:44:2a
The newer and better way is with iproute2:
# ip link set br0 address 00:0a:e7:2c:44:2a
