My experience with Cisco 9800 WLC ISSU feature

As a network engineer, I recently learned about the amazing capabilities of Cisco Catalyst 9800 Wireless Controllers to perform an In-Service Software Upgrade (ISSU) with minimum downtime during a complete wireless refresh. ISSU is a procedure to upgrade the wireless controller image to a later image while the network continues to forward traffic even during the upgrade.

I was curious to learn more about this process, so I dug into the Cisco documentation and found out that there are a few prerequisites for ISSU. The WLC must be in install mode and both the active and standby controllers must be on the same software level. Additionally, there should be no power interruption during the upgrade.

Using the Cisco DNA Center, I was able to perform an ISSU upgrade with ease. First, I checked the ISSU compatibility metrics to make sure that the device I was upgrading was supported. Then After that, I used the software download feature on DNA Center to download the image and marked it as golden. Next, I used the software activation feature to activate the image and used the show version command to verify that the image was activated. I also used a custom command to check the version before and after activation.

Finally, I used the install ISSU board command to start the upgrade process and used the show AP image upgrade command to track the percentage of APs that had been upgraded. I can also use the install ISSU abort command to manually abort the process if needed.

Overall, I was impressed by how easy it was to perform an ISSU upgrade using Cisco DNA Center. It is a great way to ensure that your wireless network is up-to-date with minimum downtime and disruption.

I highly recommend reading the Cisco documentation before attempting an ISSU upgrade. This will ensure that your WLC, APs, and source release to target release are all supported. Additionally, it is important to plan ahead and make sure you have enough time for the upgrade process. It took me around 36 minutes to complete the distribution and activation, but this could vary depending on the number of APs connected to the WLC.

The great thing about ISSU is that it intelligently picks a certain percentage of APs and disconnects them from the WLC, reboots them, and then rejoins them to the controller. This ensures that there is minimal disruption to clients as they are ported to different APs before being taken down for the new software.

I hope this article was helpful and you are now excited to perform an ISSU within your network. No one likes downtime, and with the new hardware and software, you can maintain 100% uptime and the same user experience. Checkout the demo here - ISSU@SDNTech Thank you!