17.13. Dynamically Changing a Host Physical Machine or a Network Bridge that is Attached to a Virtual NIC

This section demonstrates how to move the vNIC of a guest virtual machine from one bridge to another while the guest virtual machine is running without compromising the guest virtual machine
  1. Prepare guest virtual machine with a configuration similar to the following: 
    <interface type='bridge'>
      <mac address='52:54:00:4a:c9:5e'/>
      <source bridge='virbr0'/>
      <model type='virtio'/>
</interface>
  2. Prepare an XML file for interface update: 
    # cat br1.xml
    <interface type='bridge'>
      <mac address='52:54:00:4a:c9:5e'/>
      <source bridge='virbr1'/>
      <model type='virtio'/>
</interface>
  3. Start the guest virtual machine, confirm the guest virtual machine's network functionality, and check that the guest virtual machine's vnetX is connected to the bridge you indicated. 
    # brctl show
bridge name     bridge id               STP enabled     interfaces
virbr0          8000.5254007da9f2       yes                  virbr0-nic

vnet0
virbr1          8000.525400682996       yes                  virbr1-nic
  4. Update the guest virtual machine's network with the new interface parameters with the following command: 
    # virsh update-device test1 br1.xml 

Device updated successfully
  5. On the guest virtual machine, run service network restart. The guest virtual machine gets a new IP address for virbr1. Check the guest virtual machine's vnet0 is connected to the new bridge(virbr1) 
    # brctl show
bridge name     bridge id               STP enabled     interfaces
virbr0          8000.5254007da9f2       yes             virbr0-nic
virbr1          8000.525400682996       yes             virbr1-nic     vnet0