# Network interfaces for using Layer 2 Firewalls in Passive Firewall mode

You can configure Layer 2 Firewalls in Passive Firewall mode. In Passive Firewall mode, the engine captures network traffic for inspection but does not actively filter traffic.

The most common way to configure a Layer 2 Firewall in Passive Firewall mode is to define Capture Interfaces for listening to network traffic that does not flow through the Layer 2 Firewall. If you configure only Capture Interfaces, the engine always functions in Passive Firewall mode. You can also use a Layer 2 Firewall that has Inline Interfaces in Passive Firewall mode. To do this, you configure the engine to only log connections.