Abstract: A network security device has a local area network (LAN) interface and a wide area network (WAN) interface, with a capability to route packets of a network connection along a fast path that bypasses a network stack of an operating system of the network security device. A packet of a network connection that is received at the LAN interface is routed to a virtual network interface. A packet inspector reads the packet from the virtual network interface, inspects the packet, and writes the packet back to the virtual network interface after inspection. The packet is routed from the virtual network interface to the WAN interface, and exits the WAN interface towards the destination network address of the packet. After inspecting one or more packets of the network connection, subsequently received packets of the network connection are routed along the fast path.