(For future questions such as this, you may find you get a better
response (and lower signal-noise ratio) by asking on the recently
-created
libvirt-users@redhat.com list, as libvir-list has a very
large volume of patches and discussion about the internals of
libvirt)
On 02/08/2011 12:05 PM, Marcela Castro León wrote:
Hello
I've a lan of virtual machine configured with bridge. I've a
private lan of 4 machine, but one of them have 2 lan-card with
access to internet.
Evertything works almost fine, except that I've configured on each
guest the static configuration of the bridge with the ip address,
like this:
auto lo
iface lo inet loopback
auto eth6
iface eth6 inet static
address 192.168.1.41
network 192.168.1.0
netmask 255.255.255.0
gateway 192.168.1.10
So are you saying that you're attempting to give each guest the
*same* IP address? There's no way that can possibly work, even if
each is connected to a separate virtual network or bridge. Since the
host's IP stack can "see" all of the guests' network traffic,
regardless of the connection mode you choose, each must have a
unique IP address even if they can't see each other.
But each time I, for example, define the guest, it start with a
ascending number of interface: eth6,eth7, eth8, etc, Now is
initializing with eth12.
There must be a mixup in the explanation - I'm understanding that
you put the same config file in each guest, but each guest, when it
starts, shows a different ethernet interface in its ifconfig. That
doesn't seem right, because none of the guests know about each
other. Or are you saying something different? Where are you seeing
the "eth6", "eth7", ... "eth12"? In the guest XML config maybe?
So, it doesn't get the manual configuration I've done
on the /etc/network/interfaces.
How can avoid this way of work of the number of ethernet interface
the guest start?
Why are you doing a manual/static definition on the guest at all?
It's simpler to just leave the guest to automatically configure its
eth0, and if you really want a particular IP address for a
particular guest, handle that with a <host> element in the
<dhcp> section of the virtual network the guest is connected
to (or, if you're using a pure bridging setup, then in the static
hosts config of the dhcp server on that network).
A way i'm trying to solve is configuring the interface trough the
guest xml definition,
The guest xml interface configuration cannot be used to setup the IP
address, route, etc config of the guest. It is only used for two
things:
1) configuring what kind of hardware appears on the guest (but not
what name the guest gives to it!)
2) configuring how that hardware is connected to the physical
network (usually either via an existing bridge interface on the host
(in order for the guest to appear as if its directly connected to
the physical network), or via a "virtual network" created by libvirt
(which is really just a bridge that's not directly connected to any
physical interface, relying instead on the host's IP stack to route
packets from the guest out to the physical network.)
but the operation "define" on virsh accepted without
error the xml i've done, but the dumpxml doesn't show them, so, it
doesn't work at all.
I've followed the instruction that said the manual "Application
development guide - a guide to application development with
libvirt" on page 71.
That document is targeted towards software developers writing
applications to manage virtual guests using the libvirt API, not for
system administrators who are configuring virtual guests manually
(or, more likely, by using software that uses the libvirt API, eg
virsh or virt-manager). It likely contains more detail and less
overview than what you need, which is probably what led to the
confusion. I've included a pointer to a wiki page below that is more
the appropriate level of information (Justin, if the docs you were
working on are somewhere easily accessible, you can point to those
instead.)
The whole definition of the VM is attached, but the related to
interface is:
<interface type='bridge'>
<source bridge='br0'/>
<target dev='vnet0'/>
<protocol>
<ip address="192.168.1.41" prefix="24"/>
<route gateway="192.168.1.10"/>
</protocol>
<bridge stp="off" delay="0.01">
<interface type="ethernet" name="eth12">
<protocol>
<ip address="192.168.1.41" prefix="24"/>
<route gateway="192.168.1.10"/>
</protocol>
</interface>
</bridge>
</interface>
You are confusing the guest interface config (that is part of the
guest's XML config, and described above), and host physical
interface config (that is not in any way associated with guest
config, but instead used to configure the host's physical network
interfaces, bridges, bonds, and vlan interfaces; and nearly as
important, is not supported on Ubuntu anyway).
Actual guest interface config is *much* simpler than that.
But after define, the dumpxml only show this part:
<interface type='bridge'>
<mac address='52:54:00:3c:92:9a'/>
<source bridge='br0'/>
</interface>
That's because everything else you've put in your guest config is
not actually a part of a valid guest interface config, and so is
ignored.
I would appreciate any help to solve the question. The problem
I've is I lost the access to the guest every time the libvirt
change the name of the interface eth1,2,3, etc.
In this case I think it may be useful to start over. You've somehow
been tricked into misunderstanding the way that network
configuration in libvirt works, confusing host interface config with
guest interface config, and the resulting config bears little
resemblance to what would actually work.
==
The first step is to read this page:
http://wiki.libvirt.org/page/Networking
to get a basic overview.
==
Second step: you should decide which of the three methods of
connecting to guests to the physical network you want to use:
1) NATed
2) routed
3) bridged
The simplest is (1), and that will probably work just fine as long
as 1) you don't need incoming connections to the guests, and 2)
you're not concerned about getting the last fraction of an ounce of
performance out of the network.
Depending on which of those 3 you decide to use:
==
Third step: follow the instructions to either create a bridge
interface on the host connected to a physical network interface (for
(3)), or to create a libvirt virtual network using one of the two
modes ((1) or (2) - actually the stock libvirt config already has a
"default" network that is probably adequate for (1), and unless you
understand IP routing very well, you'll likely want to avoid (2)).
Once the physical network is setup:
==
Fourth step: define your guests. In each guest, you'll have an
<interface> element, but it will be much simpler than what
you've previously tried. For bridged mode, the interface section
would look like this:
<interface type='bridge'>
<source bridge='br0'/>
</interface>
Depending on the guest, you may want to specify what type of
hardware is presented to the guest (default is rtl, which almost
always works, but is not the best perfrorming), in particular, if
the guest supports virtio-net, you'll want to add this into the
<interface> element:
<model type='virtio'/>
For NATed or routed mode, the guest's interface definition would
look like this:
<interface type='network'>
<source network='default'/>
</interface>
(replace "default" with the name of the network you've defined, if
you've defined your own). In this case also, you can add a <model
type='...'/> if appropriate.
Note that I don't put anything in the <interface> element
about MAC address, target device, or bus address. Those are all
setup automatically by libvirt the first time you start the guest,
and it will make sure that the guests don't interfere with each
other.
==
Fifth step: only if you need a particular guest to have a particular
fixed IP address, either 1) edit the network config file on the
guest, 2) add a static host to the libvirt virtual network
definition (giving the MAC address provided to the guest by libvirt
during the initial guest startup) with a <host> element added
to the <dhcp> element of the network; details are here:
http://www.libvirt.org/formatnetwork.html
or 3) if you're using the bridged method to connect to the physical
network, again either configure the guest's own config file, or add
a static host definition to the dhcp server running on your physical
network.
If you still have problems don't hesitate to send another mail
(although, as I said at the top, sending to
libvirt-users@redhat.com
may yield better results than
libvir-list@redhat.com).