On occasions, I would like to effectively block all internet access on devices connected to a particular WLAN. If I simply turn off the WLAN, then cellular data takes over, so I'd like to keep the WLAN "connected" to the devices, but direct the device to a fake page, faulty page or similar. (It won't fool everyone during exams, quizzes, etc - but it will fool some!)
I can see that, if the ZD was a DHCP server, then I could possibly change the DNS, but that would only take effect when new IPs were handed out and anyhow, We don't use the ZD for a DHCP server.
I've tried using Device policies to shove devices onto a fake VLAN, but that actually just reverts to cellular data on devices.
Any thoughts would be appreciated - I have 2 hours before a school-wide quiz takes place, and I'd love to have it "in place" then