VNET (VIRTUAL NETWORKS)

Azure Virtual Network (often called VNET).

• Similar to VPC in AWS.
• Setup and configured by customers.
• A secure, isolated environment.
• Any VM inside the environment can talk to another VM inside without any additional security configuration.
• Nothing outside the environment can talk to anything inside the environment (without explicit configuration).
• VM can be created without a VNET
• Each VNET must be fully contained in one region.
• To connect with a VM on another VNET, then VNET to VNET private network should be configured(like VPC peering in AWS).
• Each VNET can have multiple subnets
• VNETS contain one or more subnets. By default, we get one subnet and create multiple subnets if needed.A subnet is a range of IP addresses.
• Access to subnet controlled by NSG (Network Security Groups)

• VNETs can be connected to each other (or to your on-premises network) using a virtual private network(VPN).
• Virtual Networks can be divided into subnets, Subnets are given unique IP address ranges.Smaller the number, more IP Addresses it represent.Two IP Addresses in the range will be reserved for specific purposes.So, we have 14 addresses for range of 16.
• /24 is a range of 256 (*254) addresses (i.e., 192.168.1.0 - 192.168.1.255)
• /26 is a range of 64 (*62) addresses (i.e., 192.168.1.64 - 192.168.1.127)
• /28 is a range of 16 (*14) adddresses (i.e., 192.168.1.240 - 192.168.1.255)
• Etc.
• The smallest subnet is /29 (8 addresses) and the largest is /8 (16 million addresses)
• VNETs start with a limit of 50 per subscription.Can increase to 500 upon request.
• Subnet cheat sheet: link

Official Azure Virtual Network Home Page - https://azure.microsoft.com/en-us/services/virtual-network/
Creating a Virtual Network in Azure - https://docs.microsoft.com/en-us/azure/virtual-network/virtual-networks-create-vnet-arm-pportal
Overview of Virtual Networks - https://docs.microsoft.com/en-us/azure/virtual-network/virtual-networks-overview