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:*[email protected]
[mailto:[email protected]] *On Behalf Of *Zoltan Frombach
*Sent:* Wednesday, December 9, 2015 4:24 AM
*To:* Discussion about the virtualization on CentOS
<[email protected]>
*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:*[email protected]
<mailto:[email protected]>
[mailto:[email protected]] *On Behalf Of *Zoltan Frombach
*Sent:* Wednesday, December 9, 2015 2:42 AM
*To:* Discussion about the virtualization on CentOS
<[email protected]> <mailto:[email protected]>
*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" <[email protected]
<mailto:[email protected]>> 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
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