The following key points are recommended to be considered when working with VNet2VNet connections:

• Communications between VNets is not high, as it is constrained by the VPN gateway speed
• Ensure that there are no IPs overlapping between the two VNets
• To avoid unexpected functioning of VPN gateways, avoid associating NSGs to gateway subnets
• Traffic between VNets in different regions is charged for the outbound traffic
• Traffic flows between VNets via the Microsoft Azure backbone network
• IPsec/IKE encryption is used to protect the VNet2VNet connection
• A VNet2VNet connection between public Azure VNets, and German, US Government, and Chinese Azure VNets cannot be created
• A VNet with a route-based VPN type cannot be connected to a VNet with a policy-based VPN type
• As discussed earlier, you need to create a virtual network gateway for each VNet you want to add to a VNet2VNet connection, which will incur more charges
• A gateway subnet is required for each VNet you want to build a virtual network gateway for
• VMs cannot be deployed to a gateway subnet
• Static public IP address allocation for a VPN gateway is not allowed
• Policy-based VPN is not supported for a VNet2VNet connection