Virtual Networking

Hi I am using libvrt for the first time. Im building a KVM for multiple Virtual OS instances. The problem i have is with your official documentation for Virtual Networking. https://wiki.libvirt.org/page/VirtualNetworking The following is wrong: The default mode is BRIDGE + NAT. Optional mode is ROUTING. It should be: The default mode is ROUTING + NAT. Optional mode is BRIDGE. As far as i know a bridge operates on the Layer2. IP and NAT operate on the Layer3. NAT can not operate on the L2. Please tell me that im wrong and explain how am i wrong. Best Regards