Apple introduced an iOS feature to facilitate network access when captive portals are present. This feature attempts to detect the presence of captive portal by sending a web request upon connecting to a wireless network, and directs the request to //www.apple.com/library/test/success.html

If a response is received, then Internet access is assumed and no further interaction is required. If no response is received, Internet access is assumed to be blocked by captive portal and CNA auto-launches the pseudo browser to request portal login in a controlled window.

CNA may break when redirecting to an ISE captive portal. WLC version 7.2 added a CLI command that will prevent the pseudo browser from popping up.