Can a Palo Alto Networks NGFW, when deployed on ESXi without NSX, function as a Layer 2 (Ethernet) firewall?

The correct answer emphasizes that a Palo Alto Networks Next-Generation Firewall (NGFW) can operate as a Layer 2 (Ethernet) firewall when deployed on an ESXi hypervisor, but it requires the network interface card's promiscuous mode to be enabled.

When a firewall operates in Layer 2 mode, it functions similarly to a switch, processing Ethernet frames without interfering with IP addressing. For this to occur in a virtualized environment like ESXi, promiscuous mode must be enabled on the virtual switch to allow the NGFW to receive all traffic on the network segment. This is essential because, without promiscuous mode, the virtual appliance would only see packets addressed to its own MAC address, hindering its ability to perform traffic inspection and enforcement effectively.

In contrast, other options may misinterpret the NGFW's requirements or operational modes. Some may suggest that promiscuous mode should be turned off or imply that no changes are needed in the configuration, which would limit the NGFW's functionality and prevent it from fully utilizing its Layer 2 capabilities. Hence, recognizing the necessity of enabling promiscuous mode is crucial for correct deployment and effective traffic monitoring in this scenario.