I built a captive portal (Linux Debian router),
providing a WifiHotspot based on
hostapd and iptables rules ( like this: http://www.andybev.com/index.php/Using_iptables_and_PHP_to_create_a_captive_portal ).
It works, by redirecting any request to a local welcome login page.
On Android, Kindle: the portal is detected as captive. And something happens ( notification, alert, popup...)
On iOS, the CNA (Captive Network Assistant), nothing happens. Unless I put
wispr payload in the local pages ('Reply' one, MessageType=100, code=0).
My question is: why ? Why without WispR "tag" there is no CNA ?