Configuring a Network on Azure's Classic Portal

If you have not yet configured Azure Active Directory, and are unfamiliar with the classic portal, chances are you also have not yet configured a virtual network. This should be your first step. You should also have a network (or networks) configured for your virtual machines on the primary Azure Administration portal, under your resource group. For more on configuring networks for Azure, see SoftNAS on Microsoft Azure: Managing Network Settings. Azure AD requires virtual networks configured on both the classic and the new management portal. These networks will be peered. Peering your classic and resource manager virtual networks is covered in Network Peering.

To configure a network in the classic portal is simple. Go to Networks by scrolling down the left side menu. 

As you can see, creating a network in the Classic Portal is quick and painless. Simply provide the name, the address space you would like to use, and consider your VM count for the network in question. Ensure that you select the same location (region) that your resource group will use.

Also ensure that if you have more than one subscription, that you ensure you select the same one that your resource group and associated virtual network/s use.

Provided you have a network with the same subscription and in the same region on both the classic and new Azure Management portals, you are ready to configure AD, and to peer your networks.