In ACI, which mode are the NGFW's interfaces always in?

In Application Centric Infrastructure (ACI), the interfaces of Next-Generation Firewalls (NGFWs) are always in Layer 3 (L3) mode. This is because L3 mode enables the firewall to perform IP routing, allowing it to inspect, filter, and manage traffic efficiently. In L3 mode, the firewall can analyze the packets at the network layer, making it capable of applying security policies based on IP addresses and routes.

Utilizing L3 mode facilitates the NGFW's ability to manage and secure traffic across routed networks, which is essential for modern data centers that employ large-scale automation and dynamic workloads. Firewalls in this mode can engage in advanced security functions, including intrusion detection and prevention, deep packet inspection, and the enforcement of security policies based on Layer 3 information.

The other modes, while relevant in different contexts, do not apply to the NGFW's operation within ACI. For example, L2 mode operates at the data link layer and is used for switching traffic without routing capabilities, which is not suitable for NGFW requirements. Tap mode is primarily for monitoring purposes and does not allow for traffic manipulation or intervention. Virtual Wire mode typically enables transparent inline connections without altering the IP addressing, but it is also not