Juniper Networks IDP8200 manual Normal State, NIC Bypass State, NIC State Options, Settings, Modes

Chapter 2: Hardware Overview

Table 4: NIC State Options

ACM
Settings	Modes	Availability	Description
NIC bypass	Transparent	„ Sensor failure	While sensor is active, it does not pass
	mode only	„ Graceful	NSRP packets unless Layer 2 bypass is
			enabled.
		shutdown
			When sensor becomes unavailable, ports
			mechanically join in a crossover. Traffic
			continues to flow, but sensor does not
			examine traffic.
External	Transparent	Sensor failure only	While sensor is active, it passes NSRP
bypass unit	mode only		packets even if Layer 2 bypass is disabled.
			On failure, external bypass unit passes
			traffic around the sensor.
			Note: This is a global setting. If set for any
			NIC, NSRP packets are allowed for all NICs.
NICS off	All inline	„ Sensor failure	While sensor is active, it does not pass
	modes	„ Graceful	NSRP packets unless Layer 2 bypass is
			enabled for transparent mode.
		shutdown
			When sensor fails or when the sensor
			software is shut down, NICs turn off even if
			sensor still has power.

Normal State

When the IDP is active and NICs are in the normal state, NICs only pass Layer 2 traffic if in transparent mode and if Layer 2 bypass is enabled. NSRP packets are not passed, so external bypass units do not behave correctly.

NIC Bypass State

Ethernet copper ports on the IDP 75, 250, 800, and 8200 sensors all have built-in port bypass with crossover. Port bypass only works if the sensor is configured for transparent mode. If a sensor fails or is shut down while in transparent mode, the pair of copper ports will automatically fail into a crossover “connected” state, and traffic will flow through them to and from the rest of the network without being analyzed.

NIC bypass works using a watchdog timer. Each port pair has a timer. The sensor sends each timer a reset signal every second. If a timer does not receive a reset signal for three seconds (or the configured time period), the bypass is activated. After the bypass is activated, the timer continues listening for a reset signal. When IDP becomes active again, it sends a reset signal. When the timer receives the reset signal, the bypass deactivates automatically and the sensor goes back to normal operation.

When NICs are in NIC bypass state prior to shutdown or failure, they only pass Layer 2 traffic if in transparent mode and if Layer 2 bypass is enabled. NSRP packets are not passed.

Traffic Ports (Forwarding Interfaces) „ 11