If you are using pure Azure AD (so no local Active Directory) then you can't authenticate against it using what comes with the Meraki system.   Azure AD basically requires an OUATH authenticator, which means its system requires that it's authentication web page is popped up before continuing.  Quite a painful thing to create from a splash page.   I believe some third parties like Splash Access offer a solution for doing this: https://www.splashaccess.com/cisco-meraki-azure-ad-with-splashaccess/  ... View more