In Microsoft System Center Virtual Machine Manager 2008, SCVMM added the VLAN automatically to the VM Hosts VLAN Trunk , if you added the VLAN to a Virtual Machine.
In the properties of the Virtual Machine Host under networking you have to edit the VLN Trunk.
what happens at the point you click OK here? does the host briefly reset the NIC (physical/virtual) whilst the settings are applied? Or can this change be made on the fly without the risk of all the VMs running on the host dropping briefly?
If you add all the VLANs you need it should work in the fly