Virtual Networking

[Armin Lepir]

Hi Michal

Thank you for the clarification. Also I am sorry for being a bit salty. I
will look more into the linux kernel bridge module.

Best Regards

On Wed, 26 Oct 2022, 09:10 Michal Prívozník, <mprivozn at redhat.com> wrote:

> 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 Please note that our wiki page is obsolete and we tried to move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
>
>
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