PoE switch always on

Always-on PoE, also known as perpetual PoE, ensures that connected devices continue to receive power even when the switch reboots, maintaining uninterrupted operation.

What Always-On PoE Is

Always-on PoE is a feature that allows a switch to deliver power to connected devices continuously, even during a soft reboot of the switch. Unlike standard PoE, which stops supplying power whenever the switch restarts, always-on PoE maintains power at the hardware level, independent of the switch's operating system or CPU status . This is particularly important for devices that require constant uptime, such as IP cameras, access control systems, medical monitors, or industrial sensors .

How It Works

• Soft Reboot Support: Devices connected to ports configured for always-on PoE remain powered during a soft reboot of the switch .
• Hardware-Level Power: Power delivery is maintained at the physical interface level, so devices do not experience downtime while the switch's software reloads .
• Limitations: If the switch loses main power entirely, always-on PoE cannot supply power, as it relies on the switch's internal power source .

Benefits

• Uninterrupted Device Operation: Critical devices like security cameras, electronic locks, and industrial IoT sensors continue functioning without interruption .
• Improved Reliability: Reduces downtime caused by switch reboots, firmware upgrades, or configuration changes .
• Simplified Network Management: Eliminates the need for secondary power sources or UPS systems for certain devices, reducing complexity and cost .

Configuration

• On some switches, such as the Aruba 4100i series, always-on PoE can be enabled per interface using commands like power-over-ethernet always-on 1/1 and disabled with no power-over-ethernet always-on 1/1 .
• Cisco and other vendors provide similar configuration options, often requiring setup before connecting powered devices to ensure uninterrupted power during switch reloads .

Comparison with Fast PoE

• Fast PoE: Delivers power immediately after hardware initialization, reducing the time for devices to power up during startup, but does not maintain power during a reboot .
• Always-On/Perpetual PoE: Maintains continuous power during switch reboots, ensuring devices never lose power, which is critical for high-availability environments . In summary, enabling always-on PoE on a switch is essential for networks where device uptime is critical, providing continuous power to connected devices even during software reloads or maintenance, thereby enhancing reliability and operational continuity.