Chapter 2: Hardware Overview
Table 4: NIC State Options
ACM |
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Settings | Modes | Availability | Description |
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NIC bypass | Transparent | Sensor failure | While sensor is active, it does not pass |
| mode only | Graceful | NSRP packets unless Layer 2 bypass is |
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| enabled. | |
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| shutdown | |
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| |
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| When sensor becomes unavailable, ports |
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| mechanically join in a crossover. Traffic |
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| continues to flow, but sensor does not |
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| examine traffic. |
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External | Transparent | Sensor failure only | While sensor is active, it passes NSRP |
bypass unit | mode only |
| packets even if Layer 2 bypass is disabled. |
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| On failure, external bypass unit passes |
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| traffic around the sensor. |
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| Note: This is a global setting. If set for any |
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| NIC, NSRP packets are allowed for all NICs. |
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NICS off | All inline | Sensor failure | While sensor is active, it does not pass |
| modes | Graceful | NSRP packets unless Layer 2 bypass is |
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| enabled for transparent mode. | |
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| shutdown | |
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| |
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| When sensor fails or when the sensor |
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| software is shut down, NICs turn off even if |
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| sensor still has power. |
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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
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