On 08/27/2015 08:56 PM, Spanky Horawitz wrote:

Thanks again!

Can you tell me the difference in setting things up that way as opposed to updating (in Ubuntu) /etc/network/interfaces and adding physical br(idge) interfaces? On my other test box, I setup networks the way you describe from https://help.ubuntu.com/community/KVM/Networking

The main difference between libvirt's bridges and a bridge setup as described on that page is that bridges created by libvirt will never have a physical ethernet device directly attached, so any communication to the outside from interfaces connected to a libvirt-created bridge will need to be routed at L3 by an IP stack on "something" connected directly to the bridge; that could be another guest which has multiple interfaces (as you're setting up) or it could be the host itself (when you configure an IP address on a bridge, that effectively plugs the host's IP stack into a port on the bridge).

It's possible to configure bridge interfaces with no directly attached ethernet outside the scope of libvirt in /etc/network/interfaces - just skip the "bridge_ports" line. The effect is the same, just depends on where you want your config.

-----Original Message-----
From: Laine Stump <laine@laine.org>
To: libvirt-users@redhat.com
Cc: shorawitz@gmail.com
Subject: Re: [libvirt-users] Isolated networks && test lab
Date: Thu, 27 Aug 2015 20:52:04 -0400

On 08/27/2015 08:25 PM, Spanky Horawitz wrote:

Sorry, just realized there is a VMmanager app too (free version seem to only have support for Debian 7 though.) I am using the Virtual Machine Manager GUI (virt-manager.)

virt-manager is what I'm talking about (don't know what you mean by "VMmanager"). Probably the dialogs have changed - mine is v1.2.1. 0.9.5 sounds a bit old, you should see if there is a backport of a newer version somewhere for whatever distro you're running.

Alternately, it is dirt simple to create a new network that has no IP address associated with it. Just do this:

1) create a file with these contents:

    <network>
      <name>mynetname</name>
    </network>

2) "virsh net-define filename.xml" (where filename.xml is the file containing the above XML)

3) "virsh net-autostart mynetname; virsh net-start mynetname"

(all these run as root)
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