CloudStack automatically creates and destroys interfaces bridged to VLANs on the hosts. In general the administrator does not need to manage this process.

CloudStack manages VLANs differently based on hypervisor type. For XenServer or KVM, the VLANs are created on only the hosts where they will be used and then they are destroyed when all guests that require them have been terminated or moved to another host.

For vSphere the VLANs are provisioned on all hosts in the cluster even if there is no guest running on a particular Host that requires the VLAN. This allows the administrator to perform live migration and other functions in vCenter without having to create the VLAN on the destination Host. Additionally, the VLANs are not removed from the Hosts when they are no longer needed.

You can use the same VLANs on different physical networks provided that each physical network has its own underlying layer-2 infrastructure, such as switches. For example, you can specify VLAN range 500 to 1000 while deploying physical networks A and B in an Advanced zone setup. This capability allows you to set up an additional layer-2 physical infrastructure on a different physical NIC and use the same set of VLANs if you run out of VLANs. Another advantage is that you can use the same set of IPs for different customers, each one with their own routers and the guest networks on different physical NICs.