ISE Guest certificate is not valid on android devices

[SMD28316]

I'm having an issue with wireless guest access for android devices, whenever I try to access the guest portal I get this alert in the browser:

Connection not private Something is interfering with your Wi-Fi network's security. If you continue, your data may be vulnerable to attackers.

I can click on continue and no error messages appear, but I don't think this is a normal behavior, as I have a valid certificate that is signed publicly by DigiCert. I have renewed this certificate since few weeks ago, then I started seeing the alert.

My search had led me to this defect CSCvm10640, it's related to BYOD and I'm not sure if it's related to my issue.

[Marcelo Morais]

Hi @SMD28316 ,

 an error message appears after you click Continue, for example:

NET::ERR_CERT_COMMON_NAME_INVALID

NET::ERR_CERT_AUTHORITY_INVALID

 This error can give you a hint of the problem.

Hope this helps !!!

[SMD28316]

There is no error message after clicking on continue

[Arne Bier · Accepted solution]

Hello @SMD28316 

I had a similar thing recently and it turned out that the Android devices didn't connect because the portal cert had a wildcard in the SAN. Normally this is okay and has always worked. We had to purchase new certs that contained the FQDNs in the SAN and then those Android devices connected without complaints.

We had another group of Android Devices from Oppo (a brand) that didn't associate to the open SSID unless we enabled 802.11r (Fast Roaming) - that was weird. Now I enable 802.11r jst in case and no more complaints. Android is dragging us into the 21st century kicking and screaming!