[libvirt-users] [libvirt] configuring network interface
Marcela Castro León
mcastrol at gmail.com
Fri Feb 11 10:18:44 UTC 2011
Hello
It's working now. I've put the mac address in the xml definition.
Thank you very much,
Regards.
2011/2/10 Laine Stump <laine at laine.org>
> On 02/10/2011 09:51 AM, Tanguy ROZIER wrote:
>
>> OK so he should fix the problem with libvirt to associate a fixed MAC
>> to the interface of the VM :
>>
>> <interface type='bridge'>
>> <source bridge='br0'/>
>> <mac address="00:11:22:33:44:55"/> <----------this is here :
>> you must *define* the MAC address of your interface
>> </interface>
>>
>
> As I said in my last mail, if you do not manually define a MAC address for
> an interface, libvirt will automatically generate a random mac address, and
> save it into the domain config for you, so that the 2nd and subsequent times
> you start the guest, it will use the same mac address. So, there is no
> requirement that you manually define the MAC address.
>
> For example, I just edited an existing domain config with "virsh edit
> domainname" and added this:
>
>
> <interface type='network'>
> <source network='default'/>
> <model type='virtio'/>
> </interface>
>
> Then I immediately ran "virsh dumpxml domainname", and the interface config
> had been magically transformed:
>
> <interface type='network'>
> <mac address='52:54:00:e2:75:a4'/>
> <source network='default'/>
> <model type='virtio'/>
> <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
> </interface>
>
> This mac address (and pci addressing information) is stored in the
> persistent config for the guest, so they will be the same every time the
> guest is started.
>
> If this is not happening, it's due to 1 of 3 reasons:
>
> 1) You are using a *very* old libvirt. I'm fairly certain, that it has
> auto-generated mac addresses at least since I became involved with libvirt 2
> years ago (and possibly it's always been that way).
>
> 2) The guests are being "virsh create"ed as transient guests, so that the
> auto-generated mac address is never saved. "virsh create" is the wrong tool
> for this job, a combination of "virsh define" followed by "virsh start"
> would be more appropriate.
>
> 3) there is a bug somewhere.
>
>
> 2011/2/10 Laine Stump<laine at laine.org>:
>>
>>> On 02/10/2011 08:50 AM, Tanguy ROZIER wrote:
>>>
>>>> Your problem is related to udev : every reboot of VM, udev in VM
>>>> checks the MAC address of the ethernet interface of the system to
>>>> associate it with a static name (eth0, eth1...).
>>>> If you change the MAC address of the Ethernet interface of your VM, it
>>>> will detect a new interface and associate it with a new name (ethx+1).
>>>> In order to avoid it :
>>>> try not to change the MAC address of your VM ethernet device (you can
>>>> fix it with libvirt xml),
>>>>
>>> When a domain is defined with an interface, if no mac address is
>>> supplied,
>>> libvirt will automatically generate one and write that generated mac back
>>> to
>>> the config, so that the next time the guest boots it will be presented
>>> with
>>> an ethernet having the same mac address as the previous time.
>>>
>>> How are you defining your guests? Are you perhaps using "virsh create"
>>> (but
>>> using an existing image file) to create a transient guest each time you
>>> want
>>> to boot the guest, rather than doing "virsh define" once to create a
>>> persistent guest, then using "virsh start" each time you want to boot it?
>>> You should be doing the latter - if you continuously use "virsh create",
>>> libvirt will think that it's a "throw away" guest, and won't save the
>>> config
>>> (or any changes to it), so the next time you do "virsh create", the disk
>>> image will have memory of the previous run (by having "eth0" assigned to
>>> some particular mac address), but libvirt won't have any memory of it (it
>>> thinks you're creating a brand new guest), so it will generate a new mac
>>> address for the interface, the guest will boot, see a "new" interface,
>>> notice that "eth0" is already taken, so it will use "eth1", and so on.
>>>
>>> If you actually are using "virsh define" to define a persistent guest, do
>>> a
>>> "virsh dumpxml" of the guest after you've started and destroyed it, and
>>> see
>>> if there is a mac address in the interface config. If not, that's a bug.
>>>
>>>
>>> or deactivate this mecanism in the VM : search in
>>>> /etc/udev/rules.d/70-persistent-net.rules : it calls
>>>> /lib/udev/write_net_rules at every reboot, you could chmod -x this
>>>> script in order to avoid it.
>>>>
>>> This may work (or may not - I haven't investigated), but it isn't the
>>> right
>>> way to fix this problem. It's dealing with the symptom rather than the
>>> cause.
>>>
>>>
>>> Tanguy
>>>>
>>>> 2011/2/10 Marcela Castro León<mcastrol at gmail.com>:
>>>>
>>>>> Hello Laine:
>>>>> I've revised the configuration and followed all your instructions.
>>>>> I'll try to give you a better explain of my problem.
>>>>>
>>>>> a) I need a bridged (3) configuration, because I have to connect the
>>>>> guests
>>>>> from each others. (via ssh and execute mpi). I've three hosts, each of
>>>>> one
>>>>> has at least a guest.
>>>>> I'll only explain about the configuration of one of them, because the
>>>>> problem is only related a one configuration.
>>>>> hostname=rionegro ip=192.168.1.4
>>>>> guest-name=rnompi1
>>>>>
>>>>> b) I've configured host bridge following step by step ther instruction
>>>>> on
>>>>> http://wiki.libvirt.org/page/Networking
>>>>> this is the /etc/network/config
>>>>>
>>>>> # The loopback network interface
>>>>> auto lo
>>>>> iface lo inet loopback
>>>>>
>>>>>
>>>>> auto br0
>>>>> iface br0 inet static
>>>>> address 192.168.1.4
>>>>> netmask 255.255.255.0
>>>>> network 192.168.1.0
>>>>> broadcast 192.168.1.255
>>>>> gateway 192.168.1.10
>>>>> bridge_ports eth0
>>>>> bridge_stp on
>>>>> bridge_fd 0
>>>>> bridge_maxwait 0
>>>>>
>>>>> c) this is the xml guest configuration related to the network.
>>>>>
>>>>> <interface type='bridge'>
>>>>> <source bridge='br0'/>
>>>>> </interface>
>>>>>
>>>>>
>>>>> d) But the guest doesn't get any IP automatically, and create an
>>>>> interface
>>>>> with a variable name (eth4, eth5,etch6..). I don't know how to achieve
>>>>> the
>>>>> guest don't behave like this and create always its network interface
>>>>> with
>>>>> a
>>>>> fixed name, for example, eth0).
>>>>>
>>>>> Why I ask that?
>>>>>
>>>>> if the guest created an interface with a fixed name, I would configure
>>>>> and
>>>>> static ip for the it.
>>>>> I'm attaching a printscreen "rnompi1.jpg" that show what ifconfig ahow
>>>>> on
>>>>> the guest (eth14 and without any IP). It doesn't get their host either.
>>>>>
>>>>> The only way I achieve to solve but "temporally" until reboot is
>>>>> configuring
>>>>> the guest statically using the name of the interface that has just
>>>>> up.In
>>>>> that case every works fine, and the guest can connect to all the other
>>>>> guests on the lan and others can connect to it.
>>>>> But this only works until reboot or reconfigure the guest, because each
>>>>> time
>>>>> the name of interface change, and my configuration I had done of
>>>>> /etc/network/interface didn't work any more because is related to
>>>>> another
>>>>> interface.
>>>>>
>>>>> I hope I've explained better the problem I have.
>>>>>
>>>>> Thank you very much, you've already helped too much to better
>>>>> understand
>>>>> the
>>>>> different cases of network configuration
>>>>>
>>>>> Regards.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> 2011/2/10 Marcela Castro León<mcastrol at gmail.com>
>>>>>
>>>>>> Hello Laine:
>>>>>> Thank you very much.
>>>>>> I've showed only one of the guest, each one have it's own ip address.
>>>>>> Anyway, I'll follow your advise of revise all the configuration after
>>>>>> reading the doc.
>>>>>> Thank you very much again.
>>>>>> Regards.
>>>>>>
>>>>>> 2011/2/8 Laine Stump<laine at laine.org>
>>>>>>
>>>>>>> (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 at 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 at redhat.com may yield
>>>>>>> better
>>>>>>> results than libvir-list at redhat.com).
>>>>>>>
>>>>>> _______________________________________________
>>>>> libvirt-users mailing list
>>>>> libvirt-users at redhat.com
>>>>> https://www.redhat.com/mailman/listinfo/libvirt-users
>>>>>
>>>>>
>>>>
>>>
>>
>>
>
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