Q: What are logical networks in System Center Virtual Machine Manager 2012?

A: Fabric management is a new feature in System Center Virtual Machine Manager (SCVMM) 2012. It includes management of computer, storage, and network fabrics.

As part of the network fabric management, it’s possible to define logical networks, for example your External Network, Private Network, Backup Network, and Test Network. If you have multiple data centers, these networks might actually be made up of completely different subnets.

By using a logical network, such as "External Network," it’s possible to define different IP subnets and/or VLAN IDs for the network, which can represent the various physical locations or sites where this logical network exists. These sites can then be linked to host groups reflecting your various data centers.

As part of the configuration of a logical network, the VMM administrator also defines which adapter on the virtualization hosts connects to the various logical networks.

The advantage of using the logical network is in a virtual machine (VM) template it’s possible to specify that it should connect to a certain logical network and the template will work no matter what data center it’s deployed to.

When deployed, the VM automatically is given an IP address based on the physical location for the logical network. Without using logical networks, the networking configuration would have to be changed depending on which site you deployed the VM template to.

As with most concepts in virtualization, by abstracting the physical networks we get greater flexibility.

Got technology issues? We've got technology answers. Check out John Savill's FAQs for Windows.