Overview

If your Kerio Control hardware appliance is housed in a rack or placed in a hard-to-reach location, you may want it to restart automatically after a power outage - whether planned (e.g., building maintenance) or unplanned (e.g., blackout). This article explains auto power-on behavior across Kerio Control hardware appliances and provides guidance for environments where reliable automatic recovery is required.

Auto Power-On Behavior

Kerio Control hardware appliances support automatic restart when AC power is restored, provided the power button was in the ON position at the time power was lost. This has been confirmed on current NG-series appliances and legacy appliances.

No BIOS or firmware configuration is required - this behavior is active by default.

📌 Note for older hardware models: Auto power-on behavior on earlier generation appliances may vary depending on the specific unit and firmware revision. The models that have confirmed auto power-on support:

• NG110, NG120
• NG310, NG320
• NG510, NG511, NG520, NG521
• NG720

Known Edge Case - Very Short Power Interruptions

In most outage scenarios - whether a brief flicker or an extended blackout - the appliance will shut down cleanly and restart automatically once AC power is restored.

However, in environments where power interruptions are very brief (typically under 15–20 seconds), such as:

• Solar battery-to-grid switchover events

• Generator transfer switching

• Unstable or fluctuating power supply environments

- the appliance power supply capacitors may retain enough residual charge to prevent a complete shutdown. In this scenario, the OS and firewall engine may crash and become unresponsive, but the BIOS does not register a full power loss event and therefore does not trigger the auto-restart sequence.

This is not a defect - it is a characteristic of the hardware power circuitry's behavior during marginal power events. The solutions below address this reliably.

Solutions and Best Practices

✅ Recommended: UPS (Uninterruptible Power Supply)

Connecting your Kerio Control appliance to a UPS is the most reliable solution across all scenarios and all hardware models:

• Short interruptions are bridged entirely - the appliance keeps running without any disruption

• Extended outages that fully deplete the UPS battery result in a clean, controlled shutdown; when AC power returns, the appliance auto-restarts normally

• Solar/generator environments - the UPS absorbs the switchover event, so the appliance never experiences the power glitch at all

Recommended UPS transfer time: under 10ms. Line-interactive or online double-conversion UPS models provide the best protection for network appliances.

✅ Alternative for Short-Glitch Environments: Smart PDU with Outlet Delay

If a UPS is not feasible, a managed PDU (Power Distribution Unit) with per-outlet delay timers provides an effective alternative specifically for the short-glitch edge case:

1. The PDU detects power restoration after an outage

2. It holds the appliance outlet off for a configurable delay (recommended: 30–60 seconds)

3. After the delay, it re-energises the outlet - by this point, the power supply capacitors have fully discharged

4. The appliance BIOS now detects a clean power loss and restoration cycle and restarts automatically

Compatible products include APC AP7900B/AP8941 Rack PDUs, Raritan PX3, and Eaton ePDU G3 series.

Summary

FAQ

Q1: Does my Kerio Control appliance restart automatically after a power cut?

A1: Yes, on current NG-series hardware (including NG300, NG320, NG520, NG521, NG720 and similar models). As long as the power button was in the ON position when power was lost, the appliance will restart automatically when AC power is restored.

Q2: My appliance crashes during a brief power interruption but does not restart. Why?

A2: Very short interruptions — typically under 15–20 seconds — may not fully discharge the power supply capacitors. The BIOS does not detect a complete power loss event and so does not trigger auto-restart. For example in solar panel or battery-backed installations during switchover. A UPS eliminates the problem entirely; a smart PDU with outlet delay is an effective alternative.

Q3: Does auto power-on work after a soft shutdown from the Kerio Control interface?

A3: No. A software-initiated shutdown will power off the appliance cleanly, but AC restoration alone will not trigger a restart in this case. Manual intervention or a managed UPS/PDU restart policy would be required.

Q4: Do I need to change any BIOS settings to enable auto power-on?

A4: No. On supported hardware, auto power-on after AC restoration is enabled by default and requires no configuration.

Q5: Is it safe to unplug and replug the power cable to force a restart?

A5: This can be used for brief, controlled testing purposes. It is not recommended as a routine operational practice — use the power button or the Kerio Control management interface for controlled restarts wherever possible.

Last reviewed: June 2026