Here,s why:
Multiple Availability Domains (ADs): Having resources spread across multiple ADs ensures that a failure in one AD won,t impact the entire VCN. This is crucial for achieving high availability.
Route tables with multiple next hops: This allows for redundancy in routing paths, ensuring traffic can flow even if one path becomes unavailable.
Private subnets in each AD: Just like public resources, private resources like app and DB servers benefit from being distributed across ADs for fault tolerance.
Internet Gateways in each AD: While having one Internet Gateway per AD can improve performance and availability for public resources in that specific AD, it,s not strictly necessary for overall VCN high availability. You can have a single Internet Gateway serving the entire VCN, and route traffic appropriately based on your needs.