[libvirt-users] Isolated networks && test lab

Laine Stump laine at laine.org
Fri Aug 28 13:21:38 UTC 2015


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 at laine.org 
> <mailto:Laine%20Stump%20%3claine at laine.org%3e>>
> *To*: libvirt-users at redhat.com <mailto:libvirt-users at redhat.com>
> *Cc*: shorawitz at gmail.com <mailto:shorawitz at 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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