Creating an bridged adapter

brctl vs ip

It seems that brctl cannot do vlan tagging, for which I tend to use the ip package instead if brctl.
brctl is part of bridge-utils
ip is part of iproute2. Lets start by installing required packages.

apt-get install iproute2 bridge-utils

Create an bridge on eth0 using CLI.

Notice, this will not be persistant, and be at gone reboots
If you want persistant bridges, skip this step and continue to Create persistant bridge

If you are connected through SSH on eth0, you WILL be disconnected, so please have an IRMC,ILO,IMPI or whatever in this case.
Make sure that there is no previously IP attached to this interface.

ifconfig eth0 0.0.0.0

Create an bridge named br0, and bridge it with eth0

ip link add name br0 type bridge
ip link set dev br0 up
ip link set dev eth0 master br0
ip addr add 192.168.10.100/24 dev br0

Now you should have an working bridged interface.

Create persistant bridge

To persist the bridge after reboots, is needed to add the bridge configuration to Debian's interface file.

/etc/network/interfaces
auto br0                                                                                                                                                                                                                                       
iface br0 inet static
    hwaddress ether xx:xx:xx:xx:xx:xx 
    address 192.168.10.100
    netmask 255.255.255.0
    network 192.168.10.0
    gateway 192.168.10.1
    bridge_ports eth0
    bridge_stp off 
    bridge_fd 0

Bring the new interface up

ifup br0

Notice, that the IP address should be on br0, NOT eth0.

ip addr show br0
21: br0:  mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
    inet 192.168.10.100/24 brd 192.168.10.255 scope global br0
       valid_lft forever preferred_lft forever
    inet6 fe80::ec4:7aff:fe86:a22a/64 scope link
       valid_lft forever preferred_lft forever