module mod1 {

    prefix abc;

    namespace "urn:cesnet:mod1";

    container interface {

        leaf ifType {

            type enumeration {

                enum ethernet;

                enum atm;

            }

        }

        leaf ifMTU {

            type uint32;

        }

        must "ifType != 'ethernet' or " +

             "(ifType = 'ethernet' and ifMTU = 1500)" {

            error-message "An ethernet MTU must be 1500";

        }

        must "ifType != 'atm' or " +

             "(ifType = 'atm' and ifMTU <= 17966 and ifMTU >= 64)" {

            error-message "An atm MTU must be  64 .. 17966";

            error-message "Duplicated error-message";

        }

    }

}