Lately, I have been working with many customers who are embracing Azure and its services. Therefore, I've been working on many projects where customers want to build a disaster recovery site on Azure, migrate some of their workloads to Azure, or even build some Azure VMs that can work side by side with their on-premises environment. All of these scenarios are achievable but only with the help of a Site-to-Site VPN connection, which will link Azure with on-premises. In other words, you cannot extend your on-premises to Azure without understanding Site-to-Site VPN connection.