iOS captive-portal detection on guest Wi-Fi
iOS devices reuse a cached IP address when reconnecting to a Wi-Fi network. That improves speed and battery life, but on guest networks without strict DHCP it can delay or break captive-portal detection: the device skips a fresh DHCP exchange, and the Captive Network Assistant may not open the login page.
The fix is to enable “DHCP Addr. Required” on the WLC guest SSID. The controller then blocks client traffic until a full DHCP handshake completes, so the device must obtain a fresh, valid IP (and the correct gateway and DNS) before any access. That reliably triggers the captive portal on iPhones and iPads.