Re: [libvirt-users] [libvirt] configuring network interface

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>

2011/2/10 Laine Stump&lt;laine(a)laine.org&gt;: > 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&lt;mcastrol(a)gmail.com&gt;: >>> 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&lt;mcastrol(a)gmail.com&gt; >>>> 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&lt;laine(a)laine.org&gt; >>>>> (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(a)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(a)redhat.com may yield >>>>> better >>>>> results than libvir-list(a)redhat.com). >>> _______________________________________________ >>> libvirt-users mailing list >>> libvirt-users(a)redhat.com >>> https://www.redhat.com/mailman/listinfo/libvirt-users >>> >> >