Prepare network mapping for Hyper-V VM disaster recovery to Azure

This article helps you understand and prepare for network mapping when you replicate Hyper-V VMs in System Center Virtual Machine Manager (VMM) clouds to Azure, or to a secondary site, by using the Azure Site Recovery service.

Prepare network mapping for replication to Azure

When you replicate to Azure, network mapping maps between VM networks on a source VMM server, and target Azure virtual networks. Mapping does the following:

• Network connection—Ensures that replicated Azure VMs are connected to the mapped network. All machines that fail over on the same network can connect to each other, even if they failed over in different recovery plans.
• Network gateway—If you set up a network gateway on the target Azure network, VMs can connect to other on-premises virtual machines.

Network mapping works as follows:

• You map a source VMM VM network to an Azure virtual network.
• After failover, Azure VMs in the source network connect to the mapped target virtual network.
• New VMs added to the source VM network connect to the mapped Azure network when replication occurs.
• If the target network has multiple subnets, and one of those subnets has the same name as the subnet on which the source virtual machine is located, the replica virtual machine connects to that target subnet after failover.
• If there’s no target subnet with a matching name, the virtual machine connects to the first subnet in the network.

Example

Here's an example to illustrate this mechanism. Take an organization with two locations in Beijing and Shanghai.

In this example:

• When you create a replica VM for any VM that's connected to VMNetwork1-Beijing, the replica connects to VMNetwork1-Shanghai.
• When you create a replica VM for VMNetwork2-Beijing or VMNetwork2-Shanghai, the replica doesn't connect to any network.

Here's how VMM clouds are set up in the example organization, and the logical networks associated with the clouds.

Cloud protection settings

Logical and VM network settings

Target network settings

Based on these settings, when you select the target VM network, the following table shows the choices that are available.

If the target network has multiple subnets and one of those subnets has the same name as the subnet on which the source virtual machine is located, the replica virtual machine connects to that target subnet after failover. If there's no target subnet with a matching name, the virtual machine connects to the first subnet in the network.

Failback behavior

To understand what happens during failback (reverse replication), assume that VMNetwork1-Beijing maps to VMNetwork1-Shanghai, with the following settings.

With these settings, review what happens in a couple of possible scenarios.

Next steps

• Learn about IP addressing after failover to a secondary VMM site.
• Learn about IP addressing after failover to Azure.