libvirt users - Jul 2011 - Using libvirt with a preexisting network infrastructure

I have a server running Ubuntu natty (libvirt 0.8.8) with separate
ethernet interfaces. I have created an unnumbered bridge for each
interface, these are connected to an already established network
infrastructure, with preexisting DHCP and DNS services.

I would like to handle *establishment* of these bridges outside libvirt
(via /etc/network/interfaces), but still have them defined as networks
within libvirt. So, libvirt shall not *configure* the bridges, just be
aware of their existence and connect each VM to its configured
bridge. This way I can use virt-manager/libvirt to connect my virtual
hosts to the correct network. The libvirt commands net-start,
net-destroy would become no-ops. It seems that libvirt is geared towards
handling all network configuration itself, but I do not need help from
libvirt for establishing the bridges, DHCP and DNS.

I know that I can edit the <interface> element in the VM XML-files
after creation, to assign a virtual host to a bridge, like
this:

  <interface type='bridge'>
      <source bridge='br22'/>
      ....
  </interface>

This works, but I would like to do this with libvirt mechanisms. Is this
possible?

 - Vegard V -

On 29/07/11 10:08, Vegard Vesterheim wrote:
> I have a server running Ubuntu natty (libvirt 0.8.8) with separate
> ethernet interfaces. I have created an unnumbered bridge for each
> interface, these are connected to an already established network
> infrastructure, with preexisting DHCP and DNS services.
>
> I would like to handle *establishment* of these bridges outside libvirt
> (via /etc/network/interfaces), but still have them defined as networks
> within libvirt. So, libvirt shall not *configure* the bridges, just be
> aware of their existence and connect each VM to its configured
> bridge. This way I can use virt-manager/libvirt to connect my virtual
> hosts to the correct network. The libvirt commands net-start,
> net-destroy would become no-ops. It seems that libvirt is geared towards
> handling all network configuration itself, but I do not need help from
> libvirt for establishing the bridges, DHCP and DNS.
If you want to connect your VMs to existing bridges then just ignore all 
the network stuff in libvirt and tell your VMs to connect to those 
bridges - virt-manager should offer the bridges as options when you 
create an interface and you just select the one you want.

Tom

-- 
Tom Hughes (tom at compton.nu)
http://compton.nu/