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Catalyst 9500 high-performance SVL separate upgrade

Hello experts,


We have 9500 high-performance model (c9500-48y4c) with SVL configured and need to upgrade from 16.09.04 to 16.12.04.

Per checking the document, high-performance models are not supporting ISSU method in current release of 16.09 yet so we need to do it with traditional upgrade and going to need downtime.

Restrictions and Guidelines for Performing ISSU

- On Cisco Catalyst 9500 Series Switches - High Performance, ISSU with Cisco StackWise Virtual is supported starting from Cisco IOS XE Gibraltar 16.12.1. Therefore, ISSU upgrades can be performed only starting from this release to a later release.



My challenge here is to minimize the downtime needed for upgrade during reload both switches. So I'm looking for a solution if I can separate both switches from SVL domain and upgrade them separately. My steps are like below. It can minimize downtime needed for upgrade from ~30mins to only ~5-10mins with some wiring needed.

  1. unconfigure SVL dual-active-detection, this is to allow a split-brain scenario and not putting one of them into recovery mode
  2. remove all downstream cables from standby switch - traffic will forwarded via active ones
  3. remove dual-active port and VSL ports
    • at this step, the standby switch will be split-brain and separated from SVL
    • we can do software upgrade on the standby switch while traffics still operational via active switches
  4. after completing upgrade on standby, do install commit version and perform software upgrade on active switch
  5. during the active switch reload, plug all downstream cables into standby switch - traffic interruptions will restored
    1. at this point, I'm not sure the active one will need to remove all downstream cable and VSL ports or not - to let it split-brain and able to commit version before joining SVL
    2. If it's not need to remove downstream cables, We might insert VSL ports back and let them negotiate SVL domain while it's booting
  6. Join SVL and commit version on active switch, the upgrade is complete on both switches.
  7. configure back SVL dual-active-detection ports, insert dual-active link port


In the document, while implementing Stackwise Virtual, after configuring SVL link it has mentioned about configuring dual-active-detection links and it's not saying this is optional steps so I wonder if this is required configuration for stackwise to work properly or it's just a mechanism to avoid split-brain scenario.

I'm been completing above steps for Cat6800 VSS once, but not sure if this method would be possible for C9500 Stackwise Virtual or not. So I need you guys to help checking steps and debate if there's any other better method.


Also in step 5.1/5.2, not sure if which one would be better for completing upgrade on Active switch?


Any opinion from you guys are appreiciated.


Leo Laohoo
VIP Community Legend

IMPORTANT: Do not forget to read the Release Notes.


  1. Clean up the flash: install remove inactive
  2. Copy the IOS-XE file into the active unit.
  3. Kick off Install Mode: install add file bootflash:cat9k_iosxe.16.12.04.SPA.bin activate commit
     WARNING: This command will automatically reboot both units.

IMPORTANT: Investigate if you need to apply SMU or not.

I aware that traditional method will need to reboot both units, but as I said, my challenge is to reduce downtime needed to upgrade both switches so it comes to the method like I mentioned.


How do you think if it's possible?


Leo Laohoo
VIP Community Legend

Very nice and very complicated process -- Very easy to get things wrong.  

Do note that you're going from 16.9.X to 16.12.X.  This means a mandatory microcode upgrade with will take between ten to fourteen minutes.