Re: Virtual Networking

On 10/25/22 17:03, Armin Lepir wrote: > 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 > <https://wiki.libvirt.org/page/VirtualNetworking> > Please note that our wiki page is obsolete and we tried to move everything into our knowledge base articles: https://libvirt.org/kbase/ We're keeping the wiki around though, because maybe not everything was moved. > > 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. If we'd be talking about bare metal network components then you are 100% correct. Except, the Linux bridge is more than just plain L2 bridge. It can have an IP address, route traffic, serve as network interface (when a host is sending a packet to a guest, the packet is injected into said bridge). What the wiki page is trying to say, that by default you'll get this 'default' network which uses this Linux 'bridge' + NAT. Optionally, you can define new network, or modify the existing one to switch to so called routed mode. Hope this clears things up. Michal