Box 1: 1 -
App1 will only be accessible from the internet. App1 has the following connection requirements:
* Connections to App1 must be active-active load balanced between instances.
* All connections to App1 from North America must be directed to the East US region. All other connections must be directed to the West Europe region.
App1 will have six instances: three in the East US Azure region and three in the West Europe Azure region.
Note: Azure Traffic Manager is a DNS-based traffic load balancer. This service allows you to distribute traffic to your public facing applications across the global
Azure regions.
Box 2: 2 -
For production workloads, run at least two gateway instances.
A single Application Gateway deployment can run multiple instances of the gateway.
Use one Application Gateway in East US Region, and one in the West Europe region.
Reference:
https://docs.microsoft.com/en-us/azure/architecture/high-availability/reference-architecture-traffic-manager-application-gateway
