Upgrading the IOS on Your Cisco Stacked Switch: A Step-by-Step Guide

Last updated: 19-12-2025

Cisco Stacked Switch Upgrade

Keeping your Cisco stacked switches updated with the latest IOS is essential for maintaining network security, stability, and performance. This guide walks you through upgrading a Cisco 3850 switch from IOS version 16.03.03 to 16.06.08 using TFTP or USB.

Current IOS: cat3k_caa-universalk9.16.03.03.SPA.bin
Suggested IOS: cat3k_caa-universalk9.16.06.08.SPA.bin

Cisco IOS Upgrade Diagram

Action Plan (TFTP Method)

STEP 1: Download IOS 16.6.8 and ensure sufficient flash space on all stack members.

STEP 2: Take a complete backup of the switch configuration.

STEP 3: Copy the IOS image to all stack members using TFTP.

copy tftp:cat3k_caa-universalk9.16.06.08.SPA.bin flash-1:
copy tftp:cat3k_caa-universalk9.16.06.08.SPA.bin flash-2:

STEP 4: Verify MD5 checksum.

verify /md5 flash-1:cat3k_caa-universalk9.16.06.08.SPA.bin

MD5 checksum: f288b24dbecdce481ea3578b0430b66e

STEP 5: Install the IOS package.

request platform software package install switch all file flash:cat3k_caa-universalk9.16.06.08.SPA.bin

STEP 6: Verify boot variable.

show boot system

STEP 7: Verify packages.conf.

more flash:packages.conf

STEP 8: Save configuration.

wr mem

STEP 9: Reload the stack.

reload

STEP 10: Verify IOS version after reload.

STEP 11: Clean old IOS packages.

request platform software package clean switch all file flash:

Upgrade Using USB

STEP 1: Download IOS 16.6.8 and verify flash space.

STEP 2: Take switch backup.

STEP 3: Copy IOS using USB (2/4/8GB supported).

dir flash:
dir usbflash0:
copy usbflash0:cat3k_caa-universalk9.16.06.08.SPA.bin flash-1:
copy usbflash0:cat3k_caa-universalk9.16.06.08.SPA.bin flash-2:

STEP 4: Verify MD5 checksum.

verify /md5 usbflash0:cat3k_caa-universalk9.16.06.08.SPA.bin

MD5 checksum: f288b24dbecdce481ea3578b0430b66e

STEP 5: Install the IOS package.

request platform software package install switch all file flash:cat3k_caa-universalk9.16.06.08.SPA.bin

STEP 6: Verify boot variable.

show boot system

STEP 7: Verify packages.conf.

more flash:packages.conf

STEP 8: Save configuration.

wr mem

STEP 9: Reload stack.

reload

STEP 10: Verify version after reload.

STEP 11: Clean old packages.

request platform software package clean switch all file flash:

Always keep console access and a USB drive handy during upgrades.

Rollback Plan

If the IOS upgrade fails, follow these steps to revert.

STEP 1: Reinstall the old IOS image.

request platform software package install switch all file flash:cat3k_caa-universalk9.16.03.03.SPA.bin

STEP 2: Verify the rollback.

show version

Conclusion

Upgrading the IOS on a Cisco stacked switch involves careful planning and execution. Following this guide step-by-step will help ensure a smooth upgrade process. Whether using TFTP or USB methods, it is crucial to verify all steps, especially checksums and boot variables, to prevent any issues. Always have a rollback plan in place to swiftly revert to the previous version if something goes wrong. Keeping your network equipment updated is essential for optimal performance and security.