I am setting up a new Guest network with a captive portal and it seems to all work fine except when Apple devices go to sleep.
When they come back on it isn't just a case of logging in again as it just indicates to the client that it is still connected and won't present the login page again. The Controller will show the client as auth required. So far the quickest way has been for me to delete the network on iPads and re-enter my settings or create a new profile on a Macbook and join again. I have also had some success when doing a manual DHCP refresh on my Macbook which sometimes seems to kick the Controller into action so it presents the login page to the client again. I was wondering if anyone has come across this issue before and whether it is related to the timers on the Controller (5508 running code 18.104.22.168) or - as I just read in another post by Leo - the 20 minute timeout that all Apple devices have built in to conserve battery life
Adjust your user idle timeout from 300 to 1800 and test ..
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Just to respond to this in case other people have the problem:
George's answer helped with client timeouts however I also discovered that because I was typing in my proxy settings manually as opposed to using WPAD/Option 252 the device was trying to get to the virtual address of the guest anchor controller via the proxy as opposed to being re-directed internally, i.e. the virtual interface was configured for 192.168.2.1 at the time and the iPad was trying to look for this address externally which returned nothing. The answer was to use wpad and ensure there was a null return on 192.168.2.1 so the device could re-direct internally to the web-auth page.