Re: How to make a VM guest look like just another metal machine on my LAN?

[john doe]

On 2/21/2021 9:46 AM, Steve Litt wrote:
> Hi all,

I'll answer some hints that will hopefully help you but I can't directly
answer your question.

> My LAN at home is on 192.168.0.0/24, connected to the Internet via a
> cablemodem/firewall/router/gateway at 192.168.0.1. My Daily Driver
> Desktop (DDD), which will after this be referred to as the "host" or
> "metal host" is at 192.168.0.2. I have a printer with an http interface
> at 192.168.0.13. Throughout this post I'm careful to discriminate
> between the metal host and the VM guest, which is created on the metal
> host, for all config options.
>
> What I'm trying to accomplish is to launch a VM guest (Devuan) on my
> metal host (Void Linux), such that the VM guest performs as if it were
> just another physical computer on my LAN.
>
> I've been reading and experimenting for four days and still don't have
> what I need. Here are some of the documents I've used trying to get
> this done:
>
> https://wiki.qemu.org/Documentation/Networking#User_Networking_.28SLIRP.29
>
> https://ahelpme.com/linux/howto-do-qemu-full-virtualization-with-bridged-networking/

Using a bridge is what you want.

> http://www.mpaoli.net/~root/bin/TEMPLATE
>
> https://www.debian.org/doc/manuals/debian-handbook/sect.virtualization.en.html#sect.lxc.network
>
> I'm trying to do it purely with ip commands, although I could use brctl
> if necessary. I'm staying away from virt-manager and aqemu because they
> don't work on my Void Linux metal host, and would just add even more
> variables and ambiguity.
>
> Speaking of ambiguity, every document I've read (and I've read dozens)
> has the following ambiguities:
>
> 1) When discussing a setting, they don't indicate whether that setting
>     should be on the metal host or the VM guest. Perhaps to a person who
>     thoroughly understands virtual machines, such a distinction would be
>     obvious via context, but it's not obvious to me.

The bridge will need to be setup on the host (metal host in your case).

> Based on the previously listed links, I deduce that the TAP is created
> by the guest VM, in such a way that it attaches to the bridge created on
> the metal host, and therefore I have no need to create a TAP on the
> metal host.

Libvirt or Qemu should do that for you assuming that you pass the
correct options.

> Here's my progress so far, based on the links listed above and my
> other readings and experimentation:
>
> ***
>
> I build the bridge purely with ip commands. Also, I don't mess
> with the firewall (which perhaps has been my problem all along). I'll
> investigate the firewall aspect tomorrow.

It is unlikely that you won't have to modify the fw when setting up a
bridge.

Also, are you allowing trafic from your guest to the other hosts on the
network (firewall    in the way...)?

HTH.

--
John Doe