Anand anand3g
It looks like your configuration is attaining SMSession with AuthLevel-6 when your are trying to access Authlevel-5. Hence not getting challenged.
Are you using the same HTML Forms Authentication Scheme and/OR are you using the same HTML Forms Login Page?
Both HTML Forms Authentication Scheme and Login Page need to be different, with TARGET being different too.
Authentication Level 5.
Realm : /authlevel5/*
HTML Forms Login Page : /siteminderagent/forms/auth5login.fcc
Target in Login Page : /authlevel5/landing/html
Authentication Level 6.
Realm : /authlevel6/*
HTML Forms Login Page : /siteminderagent/forms/auth6login.fcc
Target in Login Page : /authlevel6/landing/html
Regards
Hubert