Cisco Catalyst 9300 PoE Not Working: Causes, Troubleshooting & Replacement Guide

Power over Ethernet (PoE) is essential for enterprise endpoints like IP phones, wireless access points, and security cameras. When a Cisco Catalyst 9300 fails to deliver PoE, it can disrupt mission-critical services. This guide provides a systematic technical analysis, actionable troubleshooting workflow, and guidance for procurement decisions, while highlighting practical sourcing advantages.

Table of Contents

• Part 1: Common Causes of Cisco 9300 PoE Failure
• Part 2: Step-by-Step Troubleshooting Workflow
• Part 3: Hardware vs. Software Fix Decision Matrix
• Part 4: Procurement Strategy and Spare Management
• FAQ

Part 1: Common Causes of Cisco 9300 PoE Failure

The Cisco Catalyst 9300 series supports PoE+, UPoE, and UPoE+ (up to 90W). Failures typically fall into four categories:

1. PoE Budget and Power Supply Constraints

Even with high-density models, the total power draw may exceed the installed PSUs or module limits.

• Symptom: Console logs show %ILPOWER-5-ILPOWER_POWER_DENY: Interface Gi1/0/1: inline power denied. Reason: insufficient power.
• Action: Verify using the following commands:

switch# show power inline
switch# show power inline module 1

2. Protocol Negotiation Failures (CDP/LLDP)

PoE devices negotiate required power using CDP (Cisco devices) or LLDP (third-party devices). Failures occur when negotiation fails.

• Symptom: Devices intermittently reboot or fail to power on. Logs may show %ILPOWER-3-CONTROLLER_PORT_ERR.
• Action: Ensure LLDP is enabled:

config t
lldp run
interface Gi1/0/1
lldp transmit
lldp receive

3. Configuration or Software Corruption (IOS XE Bugs)

Configuration issues may set ports to power inline never or place them in err-disable state. Certain IOS XE versions can prevent PoE delivery across multiple ports or stacks. Upgrading to a recommended release often resolves these bugs.

4. Physical Layer Issues and Cabling

• Cable quality and length: Over 100 meters or high-resistance cables may cause voltage drops.
• Error logs: Frequent port plug/unplug can trigger Tstart or inrush current errors.

Part 2: Step-by-Step Troubleshooting Workflow

Step 1: Verify Interface Status

switch# show run interface 
switch# show interface status

Check that power inline never is not configured and the interface is active.

Step 2: Check PoE Budget

switch# show power inline module 

Ensure enough available wattage remains for connected PDs.

Step 3: Analyze Negotiation

switch# show cdp
switch# show lldp

Confirm non-Cisco devices negotiate correctly via LLDP.

Step 4: Deep Dive into Port Details

switch# show power inline  detail

Look at Power Negotiation Used and IEEE Class. If negotiation is None or class is n/a, protocol negotiation failed.

Step 5: Run Hardware Diagnostics (C9300)

switch# diagnostic start switch 1 test DiagPoETest
switch# show diagnostic result switch 1 test DiagPoETest

Check for . (Pass) or errors indicating PoE controller issues.

Step 6: Inspect System Logs

switch# show logging | include ILPOWER

Identify errors like ILPOWER POWER DENY (budget), CONTROLLER POST ERR (hardware), or CONTROLLER_PORT_ERR (PD not responding).

Operational Fixes

1. Enable LLDP globally and per-interface for non-Cisco devices.
2. Use 2-event classification for Class 4 devices:

   interface Gi1/0/1
   power inline port 2-event
   

3. Configure static power if negotiation fails:

   interface Gi1/0/1
   power inline static max 60000
   

Part 3: Hardware vs. Software Fix Decision Matrix

Symptom	Diagnosis	Recommended Action
StackPower shows "Shedding"	PSU limitation	Replace/add PSU (e.g., PWR-C1-1100WAC)
Block of 8 ports dead; cable OK	PoE ASIC failure	Replace switch chassis (e.g., C9300-48P)
All PoE died after IOS upgrade	Software bug	Upgrade or rollback IOS XE
Wi-Fi 6E APs won’t power	Budget/compatibility	Upgrade to UPOE/C9300-48U or higher PSU

Collect show tech-support poe and platform traces before RMA if hardware failure suspected.

Part 4: Procurement Strategy and Spare Management

In mission-critical deployments, downtime is costly. Key recommendations:

• Guaranteed Authenticity: Ensure replacement units are genuine Cisco hardware.
• Immediate Inventory: Vendors with in-stock switches, PSUs, and modules reduce downtime.
• Rapid Global Delivery: Fast shipping globally minimizes MTTR.

Router-switch Advantage:
Router-switch maintains global stock of Cisco Catalyst 9300 switches, PSUs, and network modules, offering fast dispatch, flexible payment options, and technical guidance—helping IT teams recover quickly from PoE failures.

• Pro Tip: Keep one cold spare PSU per 5 active switches for high availability.

FAQ

How can I verify PoE budget on a C9300 switch?

Use show power inline and show power inline module to check available, used, and remaining power.

Why do some non-Cisco devices fail to receive PoE?

Non-Cisco devices rely on LLDP negotiation. Ensure LLDP is enabled globally and on the specific interface.

How to distinguish a software issue from hardware failure?

Check logs for widespread PoE drops, run diagnostics (DiagPoETest), and observe if firmware upgrades resolve the issue. Hardware failure often requires RMA if diagnostic tests fail.

What is a practical procurement strategy for critical spares?

Maintain spares, source from vendors with guaranteed authenticity, global stock, and rapid delivery, such as Router-switch.