The first problem I encountered while going through this HOWTO was in trying to follow the example for the configuration of br0 in the /etc/network/interfaces examples.

Like many readers my existing configuration was being managed by NetworkManager ... and is using DHCP.  Naturally my attempt to follow the example past this point (thinking I was creating a new virtual network and chosing an suitable RFC1918 block of static addresses to assign to that) left my system disconnected from the 'net.

It appears that all I needed to do was:

1. Add an entry for eth0 identifying it as "inet manual" (presumably meaning: "managed by the bridge-utils").
2. Replace all the static addressing directives in the example with  an "inet dhcp" entry for br0
    

The results look like:

auto br0
iface   br0     inet    dhcp
        bridge_ports eth0
        bridge_fd 9
        bridge_hello 2
        bridge_maxage 12
        bridge_stp off

iface   eth0    inet manual
        # managed by bridge-utils?

Perhaps adding an alternative for those on DHCP and a link to the best info we can find on bridge-utils would help.

 The best info I was able to find so far is at: LinuxFoundation: Net:Bridge. But I didn't have to dive far into it before I figured out what I was supposed to be doing by taking a closer look at the before and "after" examples.

 I hope the maintainer of this HOWTO will read this.