Scenario:
Make: Cisco
Model: Cisco 2960 Series Switches
Mode: Command Line Interface [CLI]
Description: This article explains how to troubleshoot and fix the common PoE error %ILPOWER-3-CONTROLLER_PORT_ERR on Cisco Catalyst 2960 switches. This error typically occurs when a PoE-powered device, such as a wireless access point or IP phone, is connected to the switch. It indicates that the switch has detected an abnormal power condition on that specific port — either the connected device is drawing too much power, the cable is faulty, or the switch is unable to deliver stable PoE power. As a result, the switch’s PoE controller shuts down or resets power on the affected port to protect both the switch and the connected device. This often leads to intermittent connectivity drops, unstable LAN or wireless connections, and devices frequently going offline. In the sections below, we explore the most common causes of this error and provide practical, step-by-step solutions to resolve the %ILPOWER-3-CONTROLLER_PORT_ERR issue, helping you restore stable and reliable network connectivity.
Problem
One of the most common and frustrating issues faced in networks is when a PoE-powered device — such as a wireless access point, IP camera, or IP phone — suddenly starts fluctuating or goes intermittently offline. This results in unstable connections, frequent disconnections, and disruption of critical network services for users. When you check the logs on the Cisco Catalyst 2960 switch, you will often find repeated error messages starting with %ILPOWER-3-CONTROLLER_PORT_ERR. This error indicates that the switch’s Power over Ethernet (PoE) controller has detected a problem while trying to supply power to the connected device on that specific interface. The switch automatically takes protective action by disabling or resetting PoE on the affected port, which causes the connected device to lose power temporarily or repeatedly. As a result, the access point or other PoE device keeps rebooting or losing connectivity, leading to intermittent network outages.
Mar 26 14:57:50.864: %ILPOWER-3-CONTROLLER_PORT_ERR: Controller port error, Interface Gi1/0/1: Power Controller reports power Imax error
detected (edledge-switch)
Mar 26 14:57:51.369: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/1, changed state to down
Mar 26 14:57:52.383: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to down
Mar 26 14:57:53.864: %ILPOWER-3-CONTROLLER_PORT_ERR: Controller port error, Interface Gi1/0/4: Power Controller reports power Imax error
detected (edledge-switch)
Mar 26 14:57:54.903: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/4, changed state to down
Mar 26 14:57:54.924: %ILPOWER-7-DETECT: Interface Gi1/0/1: Power Device detected: IEEE PD
Mar 26 14:57:55.804: %ILPOWER-5-POWER_GRANTED: Interface Gi1/0/1: Power granted
Mar 26 14:57:58.933: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/4, changed state to down
Mar 26 14:57:58.957: %ILPOWER-7-DETECT: Interface Gi1/0/4: Power Device detected: IEEE PD (edledge-switch)
Mar 26 14:57:59.834: %ILPOWER-5-POWER_GRANTED: Interface Gi1/0/4: Power granted (edledge-switch)
Mar 26 14:58:01.166: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to up
Mar 26 14:58:03.183: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/4, changed state to up
Mar 26 14:58:05.119: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/4, changed state to up
Mar 26 14:58:07.126: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/4, changed state to up
Mar 26 14:58:14.043: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/1, changed state to down
Cisco syslogs follow this pattern for the error %ILPOWER-3-CONTROLLER_PORT_ERR:
- ILPOWER → the PoE subsystem (Inline Power)
- 3 → severity level 3 = error
- CONTROLLER_PORT_ERR → the PoE controller reported a port-level fault
- Usually followed by details like:
Interface gig 1/0/1: Power Controller reports power Imax error detected... reports power Tstart error detected... Power given, but Power Controller does not report Power Good... under-voltage and lockout(power rail issue)
These suffixes are important because they tell you what kind of PoE fault occurred
Root Cause
A) Over-current / Imax error (very common)
If you see “Imax error detected”, the switch believes the powered device (PD)—phone/AP/camera—drew more current than allowed (or it looked like it did). Cisco explicitly notes that this indicates the PD is drawing over-current beyond what is supported per IEEE 802.3af, and it can appear with some third‑party PDs (and in some cases due to a known IOS defect).
B) Tstart error
If you see “Tstart error detected”, PoE negotiation/startup did not complete cleanly (often due to cabling, device startup behavior, or a false-positive diagnostic/bug). Cisco community discussions describe it as a PoE protection behavior and note it can happen even with nothing connected if the port/hardware is damaged or due to software behavior.
C) Power given, but Power Good not reported / timer timed out
This means the switch attempted to apply power, but the PoE controller never saw the expected “Power Good” state within the allowed time—often cabling/PD issues, occasionally software defects on certain platforms.
D) Under-voltage / lockout (power rail issue)
Some logs indicate PoE power supply rail problems (e.g., “Vee under-voltage and lockout”), which can be caused by the PoE power supply, internal power circuitry, or sudden load changes.
Solution
Follow the steps mentioned here to resolve the issue by replacing the patch cord or changing the switch interface.
Step1: Eliminate the physical causes first
Follow the below steps to eliminate the physical cause.
- Swap the patch cord (this resolves a lot of cases)
- Try a different switchport
- If it’s a phone/AP, test with a known-good PoE injector (isolates PD vs switch)
Step2: Login
SSH onto the switch using username and password.
Step3: Identify the exact variant of the message
To identify the exact varient of the error message run the following command:
edledge-switch# show logging | include ILPOWER-3-CONTROLLER_PORT_ERR
Step4: Check PoE status and budget
Check the switch power status to ensure the switch is supplying the power
edledge-switch# sh power inline
Module Available Used Remaining
(Watts) (Watts) (Watts)
------ --------- -------- ---------
1 740.0 30.0 710.0
2 740.0 0.0 740.0
3 740.0 30.0 710.0
4 740.0 0.0 740.0
Interface Admin Oper Power Device Class Max (Watts)
--------- ------ ---------- ------- ------------------- ----- ----
Gi1/0/4 auto off 0.0 n/a n/a 30.0
Step5: System Power Status
Check the switch’s overall PoE power status by running the command shown below; If the System Power status shows “Good“, it means the switch has sufficient power available and the PoE system is operating normally.
edledge-switch# sh env power
SW PID Serial# Status Sys Pwr PoE Pwr Watts
-- ------------------ ---------- --------------- ------- ---------- --------
1 Built-in Good
Step6: Change PoE on Interface
You can manually configure the PoE settings on the affected interface, if the error persists. Change the PoE mode to auto or static (max) as needed, depending on the connected device and the nature of the error. You can configure it using the following commands:
edledge-switch#
edledge-switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
edledge-switch(config)#int gig 1/0/1
edledge-switch(config-if)#power inline auto
edledge-switch(config-if)#exit
edledge-switch(config)#exit
edledge-switch#
You could set the maximum PoE power supplied to the interface between 4,000 mW (4W) and 30,000 mW (30W), depending on the power requirements of the connected device. Use the following command in interface configuration mode:
edledge-switch#
edledge-switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
edledge-switch(config)#int gig 1/0/4
edledge-switch(config-if)#power inline static max 30000
edledge-switch(config-if)#exit
edledge-switch(config)#exit
edledge-switch#
Step7: Save
Save the configuration
edledge-switch#wr
Building configuration...
[OK]
edledge-switch#
Step8: IOS upgrade
If this still does not resolve the issue Consider IOS upgrade of Cisco 2960 standalone Switch or IOS upgrade of Cisco 2960 switch stack (if you’re on older 12.2SE). Cisco notes fixes in later releases for the bug scenario. If you’re running an older image, upgrading within your platform’s recommended train can reduce false positives
If it happens with nothing connected or stays on one port only
If the switch reports PoE controller errors even with no cable/device (or only on one physical port consistently), it can indicate port hardware damage or internal fault, and RMA/repair may be the right call. Cisco community responses highlight this possibility when errors occur without any connected cable/device.
By following the troubleshooting steps outlined in this article, you should be able to successfully resolve the %ILPOWER-3-CONTROLLER_PORT_ERR error on your Cisco 2960 switch. This will help restore stable PoE power to your connected devices, such as wireless access points, and eliminate intermittent connectivity issues. If the error persists after applying all the recommended fixes, it may indicate a hardware fault on the switch port or PoE controller, in which case you should consider replacing the faulty cable once more or opening a TAC case for further assistance.
EA00207