Select the authentication protocol method from the drop-down. The supported authentication protocol methods include PAP, CHAP, MSCHAP, and MSCHAPv2.
If you have selected the authentication protocol method as MSCHAPv2, Allow password changes check box is enabled. Selecting this checkbox allows users to change the password when the password gets expired or when the password is reset by the administrator.
In order to support CHAP authentication protocol method, user passwords must be stored using reversible encryption in the Operating System. In Windows Security policy security setting & AD users properties > Account tab, enable “Store passwords using reversible encryption”.