virtual network with qemu

marco.borsatino at marco.borsatino at
Thu May 14 13:38:15 UTC 2009

Thank you twice: the communication between 2 virtual PCs works.
Now should I configure another virtual PC as a gateway with a netmask, say, The virtual PC have a calss B netmask.
I will also try the tools I've suggested to me.
---------- Original Header -----------

>From      : "Nikos Vassiliadis" nvass9573 at
To          : "marco.borsatino at" marco.borsatino at
Cc          : freebsd-questions at
Date      : Thu, 14 May 2009 16:08:01 +0300
Subject : Re: virtual network with qemu

> marco.borsatino at wrote:
> > First, thank you. You are right, qemu has an internal DHCP server,
> > which should be perfect for me, becuse I would like to emulate a
> > network without any contact with external (real) world. The problem
> > is that my virtual PC can't ping the gateway. For my idea (this is
> > just a way to study a project for a network without a real network)
> > the communication is intended only among virtual PCs. But If I can't
> > contact the (virtual) gateway will it be possible to contact another
> > virtual PC on a different subnet? Or even on the same subnet? In my
> > idea I would like to create a little but complex net with one master
> > controller, a slave controller, a little number of client belonging
> > to different subnets. Maybe with or without a DHCP server.
> Yes, hosts on the same IP network, which of course are on the same
> broadcast domain, are able to communicate with each other with no
> other intermediates. A gateway is required only if you want to
> communicate with other networks. So, you have to create, let's say,
> 3 virtual PCs:
> 1) host_a on network A
> 2) host_b on network B
> 3) router_a on both networks A and B
> That's all.
> I guess, qemu uses the multicast solution to create virtual
> broadcast domains, like a switch does. qemu, I guess, has no
> knowledge of what happens on these ethernets, like a real ethernet
> switch. It's a real cool solution, since the user is able to
> create networks than can span several physical machines.
> Maybe you should use socket instead of mcast, don't really
> know the pros and cons of those two.
> Last but not least, since you seem to look for a learning tool, let
> me suggest two great ones:
> 1) imunes, you need vmware player for a quick start.
> 2) netkit
> I have extensively used imunes and it's great.
> You should also check netkit. In case, it matters, the latter
> is GNU/Linux based.
> HTH, Nikos

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