Power Controller Reports Power Imax Error Detected on Cisco 9300

What Does "Power Imax Error Detected" Mean?

The "Power Imax Error Detected" message on a Cisco Catalyst 9300 switch usually indicates that a PoE (Power over Ethernet) port has drawn more current than the configured or hardware-supported limit. This triggers the power controller to shut down the affected port to prevent hardware damage.

This issue often appears in environments with high-power devices like PTZ cameras, UPOE phones, or access points connected via longer cables.

Common Causes of Imax Errors on Cisco 9300

• High-power PoE device attached (e.g., UPOE device drawing more than 30W)
• Cable resistance or poor-quality wiring causing voltage drops
• Unexpected inrush current when a device boots
• IOS XE bugs or PoE firmware inconsistencies
• Incorrect port configuration or overcommitment of PoE budget

How to Check for Imax Errors

Use the following command to identify PoE-related errors:

show platform software fed switch active qos errors

Or for detailed port-specific information:

show power inline detail

Look for messages such as:

Interface Gi1/0/3
Power Controller reports power Imax error detected

This output confirms that the port has shut down due to exceeding the current threshold.

How to Fix or Prevent Power Imax Errors

1. Physically Check the Connected Device and Cable

• Try swapping in a shorter or certified Cat6/Cat6a cable.
• Test with a known-working PoE device to rule out hardware fault.

2. Limit Port Power via CLI

If using UPOE devices, limit the port to a lower maximum to avoid spikes:

interface Gi1/0/3
power inline port 2-event
power inline police
power inline static max 30000

> This limits the port to 30W (30,000 mW).

3. Update IOS XE and PoE Firmware

Check for known PoE-related bugs in your IOS XE version. If running a version prior to 17.6.x, consider upgrading:

show version
request platform software package install switch all file flash:cat9k_iosxe.<version>.bin

4. Monitor PoE Budget

Ensure the total power draw does not exceed the switch’s capacity:

show power inline police

FAQ Section

Q1: Is a Power Imax error harmful to the switch?

No permanent damage occurs; the port shuts down automatically as a safety measure.

Q2: Can I disable the Imax threshold?

Not directly, but you can adjust port power limits and policing settings to mitigate false triggers.

Q3: Does every PoE port support UPOE on the Cisco 9300?

Only UPOE-capable models and ports do. Check model specs or use show power inline.

Q4: Will firmware updates fix Imax errors?

In many cases, yes—especially if the issue stems from PoE controller bugs in earlier IOS XE versions.

Q5: How can I view all ports that experienced PoE errors?

Use show logging | include Imax or check show platform software fed switch active qos errors.