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How to Replace Power Supply on Cisco Switches: Enterprise Guide

Selene Gong

Power supply failures on Cisco switches can lead to unexpected downtime, stack desynchronization, and SLA violations. For enterprise networks, maintaining power redundancy and following a fast, safe, and standardized replacement procedure is essential. This guide walks you through the process step by step, combining practical instructions with best practices for modern networks.

Part 1: Understanding Cisco Power Supplies
Part 2: Hot-Swap vs Cold-Swap Replacement
Part 3: Step-by-Step PSU Replacement
Part 4: Post-Replacement Validation
Part 5: Best Practices & Risk Management
Part 6: FAQ

Part 1: Understanding Cisco Power Supplies

Cisco switches, including the Catalyst 3850 and 9300 series, support different PSU types depending on wattage, redundancy, and stack configuration.

Redundant PSU support: Dual PSUs can maintain uptime if one fails.
PSU identification: Always check the part number, wattage, and compatibility before replacement.
Verified Components: Large stacks across multiple sites demand consistent power and package status. Teams often rely on trusted suppliers like Router-switch for verified PSUs, ensuring replacements do not introduce instability or stack failures.

Part 2: Hot-Swap vs Cold-Swap Replacement

Before replacing a PSU, determine if your switch supports hot-swapping:

Hot-Swap: PSU can be replaced while the switch is powered on, provided a redundant PSU is active.
Cold-Swap: Requires powering down the switch before replacement.

Tip: Attempting a hot-swap on a non-hot-swappable PSU can cause outages or hardware damage. Always consult Cisco official site hardware guides for your specific model.

Part 3: Step-by-Step PSU Replacement

Follow these steps to safely replace a Cisco switch PSU. The procedure applies to most Catalyst models, such as 9300, 3850, 3750-X, and 2960-XR.

Document Existing PSU: Record model, serial number, and system load.
Plan Maintenance Window: For stack switches, schedule replacement during low traffic or activate redundant PSU.
Safety First: Use anti-static precautions. If performing a cold-swap, power down the switch.
Disconnect Cables: Remove the power cord from the PSU retainer and connector.
Remove the Faulty PSU: Press the release latch and slide the PSU out carefully.
Insert the New PSU: Slide the replacement module into the slot until flush.
Reconnect and Power On: Plug in the power cord and turn on the source. Verify the status LEDs turn green within seconds.
Final Check: Run CLI commands to verify PSU status and redundancy.

Example CLI commands to verify PSU and stack status:

Switch# show environment all
Switch# show switch
Switch# show stack-power
Switch# show environment power
Switch# show power inline

Critical Note: Do not leave a PSU slot empty for more than 90 seconds while the switch is powered to avoid overheating and airflow disruption.

Part 4: Post-Replacement Validation

Verify PSU LED indicators are green.
Use show environment all to check input voltage and redundancy.
For stacked switches, ensure all members report full redundancy.
Document the replacement for audit purposes.

Part 5: Best Practices & Risk Management

Maintain an inventory of verified PSUs from trusted suppliers like Router-switch.
Use ESD precautions when handling PSUs.
Perform periodic health checks using CLI commands to detect early PSU degradation.
Label all PSUs and track their lifecycle to prevent failures.
For large multi-site deployments, ensure all PSUs are consistent and verified to avoid stack validation errors.

Part 6: FAQ

Q1.Are Cisco switch power supplies hot-swappable?

Yes, most enterprise Cisco switches support hot-swappable PSUs. If only one PSU is active, removing it will cause the switch to shut down.

Q2.Can a power supply be replaced?

Yes, modular Cisco switches allow individual PSU replacement without replacing the entire chassis.

Q3.How do I check the power supply status?

Use commands like show environment power, show environment all, or show power inline to view operational status, input power, and wattage consumption.

Q4.How to diagnose a faulty PSU?

Check for red LEDs and review system logs for error messages such as “sustained overload condition” or “faulty”. If the switch continues running on a secondary PSU, the faulty unit will often show a “not responding” status in the CLI.

Q5.What are the signs of a failing Cisco PSU?

Amber or red LEDs, unexpected switch reloads, loss of redundancy in a stack, or power instability are key indicators.

Conclusion: Replacing a power supply on Cisco switches is straightforward when following standardized procedures. Combining careful planning, post-replacement verification, and sourcing verified PSUs from Router-switch ensures minimal downtime, maintains stack integrity, and supports enterprise network resilience.