Efficient Image Upgrade
Efficient Image upgrade is an optimized method of predownloading images to FlexConnect APs. For each Site Tag with FlexConnect APs joined, one AP per model in that Site Tag is selected as the primary AP, and downloads its image from the controller through the WAN link. Once the primary AP has the downloaded image, the APs in that Site Tag start downloading the image from the primary AP, via TFTP. At most three subordinate APs can download simultaneously from the primary. This reduces load on the WAN link.
Make sure that all APs joined via a Site Tag are at the same location, before enabling this feature.