MS-Win7 Kvm Guest Gets Dhcp From Host Bridge

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+1 to Dusty’s solution.

@OP please post the output of ‘brctl show’ see below for example.

$ /usr/sbin/brctl show bridge name bridge id STP enabled interfaces br0 8000.002590d3f56e no eth0

vnet0

In the VM definition, you need to define the VM’s NIC bonding to the bridge interface (in my case VM’s NIC is vnet0 and it is bridged to br0 which interfaces to the LAN via eth0).

Also, when you define the bridge, the host IP is assigned to the bridge device (br0) and not to the physical device eth0.

HTH,
— Arun Khan

One thought on - MS-Win7 Kvm Guest Gets Dhcp From Host Bridge

  • The root cause of the original problem was a change in the behaviour of libvirt (and the GUI of virt-manager) when creating new vms. The host system was already bridged and had other vms previously created and attached to the bridge without exhibiting this behaviour. I infer that at some point an update to libvirt altered the default configuration to always prefer NAT. A
    change that I failed to notice and was not conscious of given I had previous created vms without encountering this problem. Changing the configuration of the affected vms nic Source Device to ‘Specify shared device name’ and then specifying the Bridge Name fixed the problem.

    I have already commented elsewhere on the needlessly obtuse wording used for the Source Device when bridging is required. Why it does not say ‘Specify bridge name’ or ‘Use named bridge’ instead has not been plausibly explained by the maintainers. It is particularly vexatious given that when one selects
    ‘Specify shared device name’ the GUI immediately alters to display a text box labelled ‘Bridge name:’ Duhhh.

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