To be able to connect your own managed data centers with Azure, you have three options:
A site-to-site (S2S) VPN connection using public Internet.
A multisite VPN.
Azure ExpressRoute using a private network. This option is available if your data center is located in a facility like a co-location that offers Azure ExpressRoute. Alternatively a customer site can be connected directly to Azure using network service providers.
For a S2S VPN, a connection is made between a VPN gateway running in Azure and an on-premises VPN endpoint. Initially, when S2S VPN became available, only a single S2S VPN connection could be created. As of May 2014, this has been extended to a maximum of 10 S2S VPN connections. This enables to connect, for example, multiple offices or data centers to the same Azure Virtual Network. Note that a maximum of 10 connections share a maximum of 80 to 100 Mbps throughput.
A multisite VPN connection at the time of writing this book cannot be created using Azure Management...