
Explanation:
Box 1:

Box 2:

Box 3:

Configure a VNet to VNet connection
There are 5 sections to plan and configure. Configure each section in the order listed below:
Note: In this procedure, we'll walk you through connecting two virtual networks, VNet1 and VNet2. You'll need to be comfortable with networking in order to substitute the IP address ranges that are compatible with your network design requirements. From an Azure virtual network, connecting to another Azure virtual network is the same as connecting to an on premises network via Site-to-site (S2S) VPN.
This procedure primarily uses the Management Portal, however, you must use Microsoft Azure PowerShell cmdlets to connect the VPN gateways.
References:
http://www.virtualizationadmin.com/articles-tutorials/cloud-computing/microsoft/virtual- networks-microsoft-azure-part1.html