Re: [Qemu-discuss] A different way of networking

[Jakob Bohm]

On 29/01/2015 05:01, Gregor Szaktilla wrote:

Hi there!

When I was looking around for some documentation on how to get qemu
networking I only found guides where bridges and/or VPNs were involved.

Actually, the "bridge" involved is also part of Linux itself.
In fact on many modern distributions (such as Debian 6/7/8),
the needed bridge commands are preinstalled and simply need to
be enabled in the network config file.

Since I didn‘t want to read another manpage concerning something I
probably won‘t need anywhere else and since I had the time to think
about how things usually work, I created „my“ setup and wrote down what
I did. Starting with my notes I wrote the documentation I was missing
when I was looking around for something helpful. My setup doesn‘t need
anything else than what comes with probably any Linux installation (no
bridge, no VPN etc.).

Another advantage of my setup is that all things are tied together with
iptables rules only. A disadvantage may be that every new independent
virtual machine sits in its own (sub)net.

For example, on Debian, all you need to do is change the file
/etc/network/interfaces on the host machine from something
like:

auto eth0
iface eth0 inet ...
        ...

To something like (the ... parts are unchanged):

auto br0
iface br0 inet ...
        ...
        bridge_ports eth0
        bridge_stp on
        bridge_maxwait 0
        bridge_fd 0

Then qemu instances can simply be told to join br0, and
it'll be like they are plugged in next to the host
computer in extra ports in your home router.  No need
for special iptables rules, tun/tap devices etc. (though
you can still use iptables/ebtables if you want to block
some traffic).

I have heard that Red Hat people like much more
difficult explanations, and have even included those in
their GUI designs, but with Debian (and probably Ubuntu)
it is really this simple.

If you want to make your qemu networking without having to set up
bridging and such, my (german) guide may be helpful:
http://html.szaktilla.de/qemu

If you have any comment or suggestion please let me know.

Have fun! That‘s an order :-)

Enjoy

Jakob
-- 
Jakob Bohm, CIO, Partner, WiseMo A/S.  http://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
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