Cisco Catalyst 9500 IOS XE Upgrade and StackWise Virtual Configuration — Complete Step-by-Step Guide

Cisco Catalyst 9500 IOS XE Upgrade from version 17.18.03 to 17.18.04 using a USB flash drive, followed by StackWise Virtual (SVL) and Dual-Active Detection (DAD) configuration, is covered in this practical engineering guide.

On October 28, 2026, we performed a real IOS XE upgrade on a Cisco Catalyst C9500-24Y4C switch at a remote site. The software image was transferred from USB, verified using MD5, and installed using Cisco’s install-mode workflow.

During installation, we encountered an actual error because the running configuration had not been saved. We resolved the issue with write memory and successfully completed the upgrade.

We also cover the two-switch Stack Wise Virtual design, including physical MAC-address verification, switch renumbering, priorities 15 and 10, SVL ports 23 and 24, and DAD port 22.

Need the commands quickly? Start with the CLI reference below. For detailed explanations, troubleshooting, physical connections, screenshots, and verification, continue through the complete guide.

1. Quick CLI Reference — Cisco Catalyst 9500 IOS XE Upgrade

Step 1 — Pre-upgrade verification

terminal length 0
show version
show inventory
show boot
show install summary
show file systems
dir flash:
dir usbflash0:

Step 2 — Copy the IOS XE image from USB

copy usbflash0:cat9k_iosxe.17.18.04.SPA.bin flash:

Step 3 — Verify the image checksum

dir flash:cat9k_iosxe.17.18.04.SPA.bin
verify /md5 flash:cat9k_iosxe.17.18.04.SPA.bin

Compare the calculated checksum with Cisco’s published checksum for the exact image.

Step 4 — Save the configuration before installation

copy running-config startup-config

Step 5 — Install, activate, and commit

install add file flash:cat9k_iosxe.17.18.04.SPA.bin activate commit

Confirm the required reload during the approved maintenance window.

Step 6 — Verify after reboot

show version
show install summary
show boot
show redundancy

Expected result: IOS XE 17.18.04 running successfully, with installation state C (Activated and Committed).

Important: Actual IOS Upgrade Error Encountered at Site

After copying the IOS image and calculating its MD5 checksum, our first installation attempt failed:

[1] R0 FAILED: System configuration has been modified.
Please save configuration and resubmit command.

Root cause: The running configuration contained unsaved changes.

Solution:

write memory

Retry:

install add file flash:cat9k_iosxe.17.18.04.SPA.bin activate commit

The console subsequently confirmed:

SUCCESS: install_add_activate_commit

Engineering takeaway: Always review and save the intended configuration before starting an IOS XE installation. An image can be copied and checksum-verified successfully while installation still fails because of unsaved configuration changes.

2. Quick CLI Reference — StackWise Virtual and DAD

Deployment parameters

Domain 101 is the verified office reference value. Use the approved domain assigned to your actual deployment.

Switch 1 — Configuration reference

Identify the physical chassis and confirm its member number:

show inventory
show version
show switch

Set priority 15:

switch 1 priority 15

Configure the StackWise Virtual domain and links:

configure terminal
stackwise-virtual
 domain 101
exit
interface TwentyFiveGigE1/0/23
 stackwise-virtual link 1
exit
interface TwentyFiveGigE1/0/24
 stackwise-virtual link 1
exit
interface TwentyFiveGigE1/0/22
 stackwise-virtual dual-active-detection
end

Save the configuration:

copy running-config startup-config

Switch 2 — Renumbering and configuration reference

Identify the second physical chassis using its serial number and MAC address:

show inventory
show version
show switch

If the standalone second switch is numbered 1, renumber it:

switch 1 renumber 2

Complete the platform-required reload and confirm the member number:

show switch

After confirming member 2, set priority 10:

switch 2 priority 10

Configure the domain, SVL, and DAD interfaces:

configure terminal
stackwise-virtual
 domain 101
exit
interface TwentyFiveGigE2/0/23
 stackwise-virtual link 1
exit
interface TwentyFiveGigE2/0/24
 stackwise-virtual link 1
exit
interface TwentyFiveGigE2/0/22
 stackwise-virtual dual-active-detection
end

Save:

copy running-config startup-config

Deployment caution: These are staged configuration references, not an unattended paste-and-reload script. Verify the supported C9500-24Y4C StackWise Virtual provisioning sequence for your IOS XE release before renumbering or forming the pair. Some stages require reloads, and interface numbering must match the actual member state.

Quick SVL/DAD verification commands

show switch
show stackwise-virtual
show stackwise-virtual link
show stackwise-virtual dual-active-detection
show redundancy
show version
show running-config | section stackwise-virtual

Expected results include both members Ready, one Active and one Standby, SVL links Up/Ready, and DAD links Up without dual-active recovery.

3. Hardware and Software Environment

The recorded IOS upgrade was performed using the following equipment and software.

The switch initially reported:

Cisco IOS XE Software, Version 17.18.03
System image file is "bootflash:packages.conf"

The installation summary showed:

IMG   C    17.18.03.0.5496

The letter C indicates the active installation was committed.

4. Prepare the Switch for an Offline IOS XE Upgrade

At remote sites, network access may be unavailable. Prepare the software and recovery materials before travelling.

Recommended preparation includes the approved Cisco IOS XE image, trusted checksum, USB flash drive, console cable, configuration backup, rollback image, and relevant Cisco release documentation.

Verify storage:

show file systems
dir flash:

Verify USB detection:

dir usbflash0:

The recorded USB drive contained:

cat9k_iosxe.17.18.04.SPA.bin

The image size was:

1,249,489,705 bytes

5. Copy the IOS XE Image from USB to Bootflash

Execute:

copy usbflash0:cat9k_iosxe.17.18.04.SPA.bin flash:

Accept the default destination filename when prompted.

The actual console session reported:

1249489705 bytes copied in 44.193 secs

Verify the destination:

dir flash:cat9k_iosxe.17.18.04.SPA.bin

Do not proceed if the transfer is incomplete or the file size is unexpected.

6. Verify the IOS XE Image Using MD5

Before installing the new image, calculate its checksum:

verify /md5 flash:cat9k_iosxe.17.18.04.SPA.bin

The actual switch calculated:

verify /md5 (bootflash:cat9k_iosxe.17.18.04.SPA.bin)
= 6464ddbc29ee4ee6bac61258ee73625f

Compare this value with the trusted Cisco-published checksum for the exact image.

Important: A locally calculated checksum does not independently prove authenticity. It must match the trusted vendor value.

7. Real Site Troubleshooting — Installation Failed Because Configuration Was Not Saved

This was an actual issue encountered during our recorded upgrade.

After copying the IOS image and completing MD5 verification, we ran:

install add file flash:cat9k_iosxe.17.18.04.SPA.bin activate commit

The switch returned:

[1] R0 FAILED: System configuration has been modified.
Please save configuration and resubmit command.

The installation process stopped.

Root cause

The running configuration had been modified but had not been saved to startup configuration.

The error was not caused by the USB transfer or the MD5 calculation.

How we resolved the error

We saved the configuration:

write memory

Then repeated the installation:

install add file flash:cat9k_iosxe.17.18.04.SPA.bin activate commit

The second attempt proceeded successfully.

The installer confirmed:

SUCCESS: install_add_activate_commit

Lesson learned

Before running install add file ... activate commit, always verify that intended configuration changes have been saved.

Use:

copy running-config startup-config

If the installation reports unsaved configuration changes, review the pending changes, save the approved configuration, and retry.

8. Install IOS XE 17.18.04 and Verify After Reboot

After saving the configuration, execute:

install add file flash:cat9k_iosxe.17.18.04.SPA.bin activate commit

The install workflow adds, activates, and commits the software. A system reload is required to run the new version.

After the switch returns, verify:

show version
show install summary
show boot

The actual recording confirmed the committed package version:

IMG   C    17.18.04.0.759

The boot variable continued to use:

bootflash:packages.conf

The upgrade to IOS XE 17.18.04 was successful.

Optional inactive-package cleanup

Cisco IOS XE provides:

install remove inactive

Use this only after verifying the successful upgrade and reviewing the files selected for removal.

In the recorded session, inactive-file cleanup also removed the transferred 17.18.04 .bin file from bootflash. For offline sites, retain a verified recovery image on external media.

9. What Is Cisco StackWise Virtual?

Cisco StackWise Virtual allows two supported Catalyst switches to operate as one logical switching system.

The system has an Active switch and a Standby switch. The StackWise Virtual Link provides inter-chassis communication, while Dual-Active Detection helps identify split-brain conditions if SVL communication is lost.

For this example, the intended design is:

The SVL/DAD operational results described below come from a separately verified office pair, not from the recorded site upgrade session.

10. StackWise Virtual Physical Cabling — SVL and DAD

The reference configuration uses two SVL links and one DAD link.

Physical connection mapping

Logical connection diagram

          CISCO CATALYST C9500-24Y4C

       SWITCH 1                   SWITCH 2
       Member 1                   Member 2
       Priority 15                Priority 10

       Port 23 ================= Port 23
                     SVL 1

       Port 24 ================= Port 24
                     SVL 2

       Port 22 ----------------- Port 22
                      DAD

The diagram represents the intended reference cabling. Confirm actual physical connections at the rack before activation.

Use supported optics and cable types. Verify fiber polarity, link speed, transceiver compatibility, and interface status.

11. Identify Switch 1 and Switch 2 Before Renumbering

Before assigning member numbers, identify both physical chassis.

Run:

show inventory
show version
show switch

Record the serial number, MAC address, physical rack position, and current member number.

In our deployment, both switches were physically identified and checked against their MAC addresses before renumbering.

The intended final member assignments were:

• Switch 1: Member 1, priority 15.
• Switch 2: Member 2, priority 10.

This step helps prevent the wrong chassis from receiving the wrong logical identity.

12. Configure Switch Numbering and Priority

The second standalone switch may initially appear as member 1.

If renumbering is required, use the supported procedure:

switch 1 renumber 2

Complete the required reload and verify the resulting member number:

show switch

After the member numbers are correct, assign priorities.

For Switch 1:

switch 1 priority 15

For Switch 2:

switch 2 priority 10

Priority influences the election preference. It does not automatically force an already established Active switch to change roles.

13. Configure StackWise Virtual Domain and SVL Interfaces

Both switches must use the same approved domain.

Switch 1

configure terminal
stackwise-virtual
 domain 101
exit
interface TwentyFiveGigE1/0/23
 stackwise-virtual link 1
exit
interface TwentyFiveGigE1/0/24
 stackwise-virtual link 1
end

Switch 2

After confirming the switch is member 2:

configure terminal
stackwise-virtual
 domain 101
exit
interface TwentyFiveGigE2/0/23
 stackwise-virtual link 1
exit
interface TwentyFiveGigE2/0/24
 stackwise-virtual link 1
end

Use the domain number approved for your environment. Domain 101 is the office reference value, not a universal requirement.

14. Configure Dual-Active Detection on Port 22

Dual-Active Detection is an important protection mechanism for StackWise Virtual deployments.

Switch 1

configure terminal
interface TwentyFiveGigE1/0/22
 stackwise-virtual dual-active-detection
end

Switch 2

configure terminal
interface TwentyFiveGigE2/0/22
 stackwise-virtual dual-active-detection
end

Save the approved configuration:

copy running-config startup-config

Follow the platform-specific StackWise Virtual activation and reload procedure.

15. Verify StackWise Virtual, SVL and DAD

After formation and reload, verify the operational state.

Verify both members

show switch

Expected: Two members, one Active and one Standby, both Ready.

Verify StackWise Virtual configuration

show stackwise-virtual

Confirm the domain and configured interfaces.

Verify SVL links

show stackwise-virtual link

The verified office setup reported Up/Ready for:

TwentyFiveGigE1/0/23
TwentyFiveGigE1/0/24
TwentyFiveGigE2/0/23
TwentyFiveGigE2/0/24

Verify Dual-Active Detection

show stackwise-virtual dual-active-detection

The verified office setup reported both DAD interfaces Up, with no dual-active recovery condition.

Verify redundancy

show redundancy

Confirm the intended Active/Standby state.

Verify saved configuration

show running-config | section stackwise-virtual

16. Common Troubleshooting Scenarios

Do not perform disruptive SVL-failure or switchover testing on production equipment without an approved maintenance plan.

17. Final Engineering Verification Checklist

Before handover, verify:

• Both physical chassis identities and MAC addresses match the deployment records.
• Switch 1 is member 1 with priority 15.
• Switch 2 is member 2 with priority 10.
• Both switches run compatible, approved IOS XE versions.
• The software installation is committed.
• The boot variable is correct.
• SVL ports 23 and 24 are operational.
• DAD port 22 is operational on both switches.
• Both members are Ready.
• Active/Standby redundancy is healthy.
• Running configurations are saved.
• Console logs and screenshots are retained.
• Offline recovery media and backups are available.

18. Related HG IT Solutions Technical Articles

Explore these related networking and infrastructure guides from HG IT Solutions.

Cisco Nexus 93180YC-FX3 NX-OS Upgrade Using USB — A related practical guide for software upgrades on Cisco Nexus switches.

Cisco Catalyst 2960-X Factory Reset and Bootloader Recovery — Learn Cisco switch recovery, bootloader operations and configuration reset procedures.

Single-Mode vs Multimode Fiber — Understand fiber selection for network and data center connections.

OM3 vs OM4 vs OM5 Fiber — Compare multimode fiber types for high-speed network applications.

Network Device Security — Review SSH, SNMP and device-hardening practices.

Data Center Rack Installation Checklist — Practical physical-infrastructure checks before installing network equipment.

19. Official Cisco Documentation

Always confirm release-specific support and command behavior against official Cisco documentation.

Cisco — Upgrading Catalyst 9500 Switches

Cisco — Configuring StackWise Virtual on Catalyst 9500

The second reference is from the 17.17 configuration guide. Check the documentation applicable to your exact 17.18.x release before executing the deployment procedure.

Frequently Asked Questions

Can I upgrade Cisco Catalyst 9500 IOS XE without internet access?

Yes. The recorded deployment successfully transferred the image using USB and installed it locally.

Why did the IOS XE installation fail after MD5 verification?

The switch detected unsaved configuration changes. Saving the configuration with write memory resolved the error.

Does installing IOS XE require a reboot?

Yes. Activating the new IOS XE software requires the appropriate system reload.

Why do we renumber the second switch?

StackWise Virtual requires the intended member identities to be established correctly. The second chassis is assigned member 2.

Why use priority 15 on Switch 1 and 10 on Switch 2?

These values provide the intended election preference. They do not guarantee an immediate change in Active role.

Why use two SVL connections?

Multiple supported SVL interfaces provide additional interconnect capacity and resilience.

Why is Dual-Active Detection important?

DAD helps identify split-brain conditions if StackWise Virtual communication is lost.

How can I verify that StackWise Virtual is healthy?

Use show switch, show stackwise-virtual link, show stackwise-virtual dual-active-detection, and show redundancy.

Conclusion

A successful Cisco Catalyst 9500 IOS XE Upgrade involves much more than transferring a software image. Engineers must validate the image, save the configuration, complete the installation and verify the running software after reboot.

Our actual site upgrade from IOS XE 17.18.03 to 17.18.04 also demonstrated a useful troubleshooting lesson: even after a successful USB transfer and MD5 calculation, an unsaved running configuration can prevent installation.

For StackWise Virtual, accurate physical switch identification, member numbering, priorities, SVL connectivity, DAD protection and final verification are essential for a reliable deployment.

HG IT Solutions — Build • Connect • Automate

ABOUT THE AUTHOR

Haider Ali

IT Infrastructure & Data Center Professional

Haider Ali is an IT Infrastructure & Data Center Professional with over 10 years of hands-on experience in networking, structured cabling, fiber optics, data center infrastructure, and IT implementation projects. He shares practical guides, field-tested troubleshooting methods, and real-world infrastructure insights based on project experience.

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