Date: Thu, 14 May 2009 16:08:01 +0300 From: Nikos Vassiliadis <nvass9573@gmx.com> To: "marco.borsatino@poste.it" <marco.borsatino@poste.it> Cc: freebsd-questions@freebsd.org Subject: Re: virtual network with qemu Message-ID: <4A0C17B1.5060308@gmx.com> In-Reply-To: <KJMTPH$2D2A1378CB676588DEE0977D130EFCFA@poste.it> References: <KJMTPH$2D2A1378CB676588DEE0977D130EFCFA@poste.it>
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marco.borsatino@poste.it 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. http://www.imunes.net/virtnet/ 2) netkit http://wiki.netkit.org/index.php/Download_Official 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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