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[Archive] WLA upgrade issues when upgrading a WLC WLAN controller that has WLA devices at remote sites

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Article ID: KB24186 KB Last Updated: 10 Oct 2020Version: 2.0
Summary:
This article describes the issue of WLA upgrade issues, when upgrading a WLC WLAN controller, which has WLA devices at remote sites.
Symptoms:

 When a WLC is upgraded, it will go through a reboot process and then boot to the new image.  After this reboot, when the WLA devices contact the WLC to boot up, they will be instructed of the upgrade and they will in turn begin to download the new WLA code from the WLC.  

This download and configuration process for the WLA devices tend to consume more bandwidth and resources, as compared to when the WLAs are already up and running.

In certain deployments, it has been observed that WLAs deployed at remote sites and connecting over WAN/VPN links, may experience issues in downloading the new WLA image; especially if the upgraded image is a large delta from the running image (for example: running image on WLA is 7.0 and new image on WLC is 7.6). What may be seen in these scenarios is the WLAs at the remote site initiating their image download from the WLC; but the image download fails and/or times out.

Cause:
  • When WLAs are deployed at remote locations, they are often configured to utilize a local-switching configuration, so that the user traffic stays at the remote site and the WLA only needs to send back to the WLC various status updates and client authentication frames.  

  • As the WLA and WLC are exchanging very little traffic in this state, they can often work quite well over a low bandwidth or lossy connection.  

  • However, the same WAN/VPN connection may become an issue, when the WLA is required to download a new image file from the WLC; post upgrade.
Solution:
Some of the solutions for these remote upgrade issues are:
 
  • Performing the upgrade in a window, in which the WLAs should be able to consume the majority of the bandwidth on the WAN/VPN link

  • Ensure that the WLAs are performing a minimal upgrade (for example: instead of upgrading from 7.0 to 7.6, consider upgrading 7.0 to 7.3, 7.5, or 7.6 and ensure that all APs are upgraded and booted; before performing the next upgrade).

  • If the WAN/VPN link has low bandwidth, try to allow only one of the remote APs to upgrade at a time, by disabling the PoE or switch port of the other remote APs.
Modification History:
2020-10-10: Archived article.
 
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