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3.4.2. Power and Environmental Considerations
Power Components:
| Component | Function |
|---|---|
| UPS (Uninterruptible Power Supply) | Battery backup for short outages; clean shutdown time |
| PDU (Power Distribution Unit) | Distributes power to rack equipment |
| Generator | Extended backup during prolonged outages |
⚠️ Exam Pattern: For preventing brief disruptions (< 15 minutes), UPS is the answer. For extended outages, generators are needed. UPS bridges the gap while generators start (10-30 seconds).
PoE (Power over Ethernet): The switch (or an injector) powers devices such as IP phones, APs and cameras over the data cable.
| Standard | Name | Max power at the switch port |
|---|---|---|
| 802.3af | PoE | 15.4 W |
| 802.3at | PoE+ | 30 W |
| 802.3bt Type 3 | PoE++ | 60 W |
| 802.3bt Type 4 | PoE++ | 90 W |
Environmental:
- Temperature: Equipment operating range typically 64-75°F (18-24°C)
- Humidity: Too high causes condensation; too low causes static discharge
- Fire suppression: Clean agent systems (FM-200, Novec, Inergen) don't damage equipment like water sprinklers would
- Grounding: Bond racks and equipment to earth ground so fault current has a safe path. It is a safety measure—protecting people from shock and equipment from electrical faults—not a performance one
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Written byAlvin Varughese
Founder•20 professional certifications