BTW, adding a 2nd virtual nic to a guest can also be done with command line tools (I just googled this for you) : https://kashyapc.fedorapeople.org/virt/add-network-card-in-guest.txt ( It came up as 1st result when I searched for: virsh add network interface to existing guest ) But if you look at the bottom of this guide, they also mention that if something goes wrong, they resort to using virsh edit just like I suggested to you. See, I prefer to edit a configuration file rather then issuing long and complicated commands on the CLI. However, being able to add a 2nd nic to a live guest is nice though and that could only be achieved with the CLI command. As you can see, you can even add nic's to a VM without having to reboot it. Zoltan On 12/9/2015 10:58 AM, Howard Leadmon wrote: > > How do you decide what MAC address to use for that VM interface? As > I just tried to change the MAC to some other value close, like I made > '52:54:00:34:e1:21' into say '52:54:00:34:e1:32', and when I try and > load it in, I get the following: > > error: XML error: Attempted double use of PCI Address '0:0:4.0' > > Here is one of my network entries: > > <interface type='bridge'> > > <mac address='52:54:00:34:e1:21'/> > > <source bridge='br1'/> > > <model type='virtio'/> > > <address type='pci' domain='0x0000' bus='0x00' slot='0x04' > function='0x0'/> > > </interface> > > --- > > Howard > > *From:*centos-virt-bounces at centos.org > [mailto:centos-virt-bounces at centos.org] *On Behalf Of *Zoltan Frombach > *Sent:* Wednesday, December 9, 2015 4:24 AM > *To:* Discussion about the virtualization on CentOS > <centos-virt at centos.org> > *Subject:* Re: [CentOS-virt] How to manually add a new interface to a > bridge device? > > > You most definitely do not need to destroy and re-create a VM just to > add a 2nd network interface. > > I don't think those vnet interfaces got created by the host OS. I > believe those are created by KVM (or libvirt) when you start a VM. I > could be wrong though. But I just checked on my CentOS 6 KVM host > machine and I see as many vnet interfaces as many VMs are currently > running (or if one VM has two virtual network cards then of course > that VM results two vnet interfaces shown on the host). Here the > relevant part from one such VM's XML file (those XML files are under > the /etc/libvirt/qemu directory on my CentOS host ) : > > <interface type='bridge'> > <mac address='00:16:36:e2:20:ea'/> > <source bridge='br0'/> > <model type='virtio'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x03' > function='0x0'/> > </interface> > <interface type='bridge'> > <mac address='00:16:36:e2:20:eb'/> > <source bridge='br600'/> > <model type='virtio'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x06' > function='0x0'/> > </interface> > > As you can see, there are two interfaces defined in this VM's XML > file. One is connected to the host's br0 interface and the 2nd is > connected to the host's br600 interface. You must make sure that all > your mac addesses are unique on your network though!! > > After editing a VM's XML file with your favorite editor, you need to > execute this command: > virsh define /etc/libvirt/qemu//your-vm-name/.xml > or just simply use this editor: > virsh edit /your-vm-name/ > (but I hate vi, so I use my favorite editor and when I finished > editing I just run virsh define.) > > I edited VM's XML files many times and I can add/remove virtual > network cards without problems. > > Zoltan > > On 12/9/2015 9:55 AM, Howard Leadmon wrote: > > Tried that as well, but this has to be something that gets set at > the OS level and loaded, as if you look at dmesg output, you can > see all the vnet?? nodes as the OS comes online. So the > question is, what is virt-install doing that creates the needed > vnet interface that is part of the bridge. I really had to kill > and reload the VM just to load a second interface.. > > --- > > Howard Leadmon > > *From:*centos-virt-bounces at centos.org > <mailto:centos-virt-bounces at centos.org> > [mailto:centos-virt-bounces at centos.org] *On Behalf Of *Zoltan Frombach > *Sent:* Wednesday, December 9, 2015 2:42 AM > *To:* Discussion about the virtualization on CentOS > <centos-virt at centos.org> <mailto:centos-virt at centos.org> > *Subject:* Re: [CentOS-virt] How to manually add a new interface > to a bridge device? > > I would stop the VM, edit its definition file (that's an XML file) > and then start it up. But be careful: After you edit the XML file, > you need to execute a command so KVM re-reads that file. I forgot > that command, but you can look it up on Google. > > On Dec 9, 2015 7:52 AM, "Howard Leadmon" <howard at leadmon.net > <mailto:howard at leadmon.net>> wrote: > > Maybe my google-fu is failing me, but I have spent the past > couple hours looking at how to add a vnet? Device to my KVM > host running CentOS 6, and for the life of me I can’t get this > going. > > From all my research if I want to add a device I should just > do ‘brctl addif br1 vnet14’ if I want to add a vnet14 to > bridge br1. When I do this, I get: > > # brctl addif br0 vnet14 > > interface vnet14 does not exist! > > If I run a ‘brctl show’ I get the following: > > # brctl show > > bridge name bridge id STP enabled interfaces > > br0 8000.00237dd22a4c no eth0 > > vnet0 > > vnet10 > > vnet11 > > vnet13 > > vnet2 > > vnet3 > > vnet4 > > vnet6 > > vnet8 > > br1 8000.00237dd22a50 no eth1 > > vnet1 > > vnet12 > > vnet5 > > vnet7 > > vnet9 > > Needless to say the existing vnet?? Devices are in use on > guest VM’s currently. > > When I create a new VM using virt-install, I usually add the > following to my command line: > > --network=bridge:br0 --network=bridge:br1 > > I messed up building a new VM, and only added the br0 > interface to the VM, but need the br1 interface as well. So > my question is, or a pointer to how I can add that br1 > interface to my existing VM, and create the needed vnet14 > interface for it to attach to? > > If anyone can explain how to do this, or give me a good > pointer on where the info is on how to do this, it would sure > be a huge help.. > > Thanks… > > --- > > Howard Leadmon > > > _______________________________________________ > CentOS-virt mailing list > CentOS-virt at centos.org <mailto:CentOS-virt at centos.org> > https://lists.centos.org/mailman/listinfo/centos-virt > > > > > _______________________________________________ > > CentOS-virt mailing list > > CentOS-virt at centos.org <mailto:CentOS-virt at centos.org> > > https://lists.centos.org/mailman/listinfo/centos-virt > > > > _______________________________________________ > CentOS-virt mailing list > CentOS-virt at centos.org > https://lists.centos.org/mailman/listinfo/centos-virt -------------- next part -------------- An HTML attachment was scrubbed... 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