Re: [Qemu-discuss] virt-install and bridged interfaces

[Donald R Laster Jr]

Dan MacDonald wrote on 11/28/2017 01:57 PM:
> Hi qemu list
>
> I have a CentOS 6 disk image I created with Packer which I would like
> to use with a network manager bridged network interface (virbr0) under
> libvirt/KVW/qemu.
>
> I can run the image under qemu/KVM with working bridged networking
> using a command such as this:
>
> qemu-system-x86_64 -enable-kvm -cpu host -m 1024 -net nic,model=virtio
> -net bridge,br=virbr0,helper=/usr/lib/qemu/qemu-bridge-helper -drive
> file=c6test,if=virtio
>
> Despite the two -net options used, only one net interface is present
> on the VM and it gets assigned a local IP which I can ping from my
> host. This is what I'm hoping to achieve but I have not been able to
> so far when importing the image into libvirt using virt-install. I
> have been trying many variations upon a command like this:
>
> virt-install -n centos6test -r 1024 --connect qemu:///system
> --os-type=linux --cpu host --os-variant=rhel6 --disk
> /home/dan/PackerTest/output_centos6test/c6test,device=disk,bus=virtio
> --network bridge=virbr0 --vnc --noautoconsole --import
>
> I have also tried defining a bridged network with virsh, like so:
>
> <network>
>    <name>hostbridge</name>
>    <forward mode="bridge"/>
>    <bridge name="virbr0"/>
> </network>
>
>
> Then importing that with `virsh net-define` and setting the network
> device to use that virsh network. I've also tried using two net
> devices, one bridged and one not etc etc but nothing has worked for me
> so far in that none of the interfaces ever get assigned an address
> after being imported into libvirt and started with virt-install whilst
> everything works fine if I just run the image with the first qemu
> command I gave.
>
> I would like to be able to control my VM with virsh but this issue is
> stopping me. I'm running Ubuntu 17.10 on the host.
>
> Thanks for your help
>
> Dan

Dan,

  You may need to add a second set of this command set:

        -net nic,model=virtio
        -net bridge,br=virbr0,helper=/usr/lib/qemu/qemu-bridge-helper

On my systems that run the VMs when I want two Ethernet device I have the 
following:

        -net nic,macaddr=52:54:00:10:01:2E,vlan=0,model=e1000
        -net tap,vlan=0,helper=/usr/libexec/qemu-bridge-helper

        -net nic,macaddr=52:54:00:10:01:23,vlan=0,model=e1000
        -net tap,vlan=0,helper=/usr/libexec/qemu-bridge-helper

I am still running an older version of QEMU since it is doing everything I need without 
any problems so the "-net tap" might not be correct for what you are doing.  So 
I would try the following:

        -net nic,model=virtio
        -net bridge,br=virbr0,helper=/usr/lib/qemu/qemu-bridge-helper

        -net nic,model=virtio
        -net bridge,br=virbr0,helper=/usr/lib/qemu/qemu-bridge-helper

when you start the VM (yes, a duplicate of the -net commands).

  Depending upon your environment setting the MAC address might be useful as 
well.  The MAC address prefix of 52:54:00 in the options above were selected 
based what was being used in a virtual machine environment that supposedly does 
not conflict with physical/real hardware MAC addresses 4 or 5 years ago.  The 
last 3 octets of the MAC correspond to the last 3 octets of the intended IPv4 
address of the network interface inside of the VM.  It helps prevents any 
potential conflicts with MACs being generated on the systems running VMs.

  A quick check has indicated the prefix 52:54:00 is used by "Realtek/Uptech?" 
so you might want to use a different prefix.  A check at https://code.wireshark.org 
indicates 00:00:6C, 00:01:01, and 00:05:78 are 3 of around 250 or so private MAC address 
prefixes (word Private in the list).

  But I do believe you need to add the second "-net nic" set of options.

   Don