In a shared VPC, what is essential for managing network traffic effectively?

In the context of a shared VPC, configuring Shared VPC firewall rules is essential for managing network traffic effectively. Firewall rules determine what network traffic is allowed or denied in the VPC, thus acting as a critical layer of security and traffic management. By defining specific rules based on protocols, ports, and IP ranges, organizations can effectively control both ingress and egress traffic. This allows for the protection of resources within the VPC and ensures that only authorized traffic is allowed, enhancing the overall security posture of the environment.

While other choices involve aspects of security and traffic management, they do not provide the foundational control over network traffic flow that Shared VPC firewall rules do. IAM for network permissions is important for managing who has access to network resources but does not directly filter or manage the actual network traffic itself. Enabling Google Cloud Armor offers protection against DDoS attacks but does not replace the need for granular traffic management provided by firewall rules. Outlining a routing configuration is vital for directing traffic appropriately within the network, but without the accompanying firewall rules, there would be no control over what traffic is permitted through those routes. Therefore, configuring Shared VPC firewall rules is the most critical aspect of managing network traffic within a shared VPC setup.