Ok, once you get a grasp of it, I'm sure you'll find it pretty simple :) Install kvm + virt-manager + libvirt, setup a bridge, use virt-manager to create a new virtual machine which uses the bridge. Now you're done, nothing more needed.
The problem being is that I have already done all that and it simply does not work as expected. So I infer that there a few important details that everyone is leaving out of their descriptions, possibly because they assume them as preconditions.
Hmm, try to have a look at this: http://www.linux-kvm.com/content/using-bridged-networking-virt-manager
Like shown in the screenshot in section 4, you should select "Shared physical device" and then select your bridge in the drop-down menu. This should NOT give you usermode network (a 192.168.122.x address), this should instead connect the virtual machine to your network, meaning you can request a DHCP address if you have a DHCP server or assign a static IP inside the virtual machine.
Best Regards Kenni Lund