This information give you a clue how the N4100 act with 220.127.116.11 for Captive Portal
Most recently, it seems that our older N4100 units encounter issues where clients instead of redirected to the captive portal are prompted with warning message that the connection is not secure.
This is due to the redirect being set to IP address 18.104.22.168 back then, which by now is reserved for the Cloudflare DNS server.
The solution to this issue is, to either create yourself a certificate according to the SOP guide (requires Linux machine) attached to this article.
For customers who do not have this option, we have already created a certificate that can be implemented, which is also linked to this article.
Private key of the certificate is 12345
Private Key File = private.key
Certificate File = Certificate.crt
You also need to set the SSL login page enabled on the N4100, screenshot below:
Some of the latest Android devices will still show a "not secure" message after you uploaded the new certificate and applied the settings as mentioned above.
Here is what you have to do:
1. Factory Reset
2. Upload of the certificate and configuration as mentioned in the KB article
3. Configuration of the hot spot
IMPORTANT: Do not apply the old config after factory reset. This will NOT work for this case.