# File lib/cidr.rb, line 1698
    def set_wildcard_mask(mask, bit_flipped=false)
        netmask_int = nil
        if (mask.kind_of?(Integer))
            NetAddr.validate_ip_int(mask,@version)
            netmask_int = mask
        else
            begin
                NetAddr.validate_ip_str(mask,@version)
                netmask_int = NetAddr.ip_str_to_int(mask, @version)
            rescue NetAddr::ValidationError
                raise NetAddr::ValidationError, "Wildcard Mask must be a valid IPv#{@version} address."
            end
        end
        netmask_int = ~netmask_int if (bit_flipped)
        @wildcard_mask = netmask_int

        return(nil)
    end