Hi Daniel
Now the network is clear let's have a second look at your problem:
You wrote:
>>>> I´m fighting with the authentication method here. I only need that the student sit in the chair, put her/his email and a password, self registration
and later:
>> I could manage it and after some core hacks, I could make the registration fluid.
>> Now, the user just put the email and password. Then, in the registration form, put the name, surname, email and, a custom field created by me called DNI (Document National Identity). All of the rest fields, I hide them (through commented lines in userlib.php, or editadvance_form, I dont remeber well)
I understand that you've solved the problem by editing Moodle code. I believe that very well, and in addtion I also believe that it is the beginning of some future problems! Can you tell why your Moodle can not do something as basic as the e-mail based user registration? Not because the users don't have access to their maiboxes without Internet?
P.S. To finish the discussion of Moodlebox as substitution to the Mikrotik: If you want to disconnect the netbooks from the Internet, just pull the ethernet plug from the Moodlebox. To give the Prof. Internet plug the cable to his notebook. Then it becomes almost the same as your present setup (sketch 1), Raspberry Pi replacing the Mikrotik, except that the web server now runs not in the Prof's notebook but in the Raspberry Pi.
I´m not using Email Based user Registration, because as I said before, the netbooks are not connect through internet. And, something important, all of the police man in Argentina do not know well using technology (email, internet, even write with a keyboard). I´m talking about people over 40 years old. They are the most when dingo the promotion exam.
Also, they have 20 minutes to do the exam. Imagine 50 men/woman trying to login with the other authentication method? Wait for each one recieve the confirmation email, etc. No way!
So, I tried to do it simple. Mail and a generic password that when they type it, just create the account. Then, Simply type name, surname, email (I couldnt delete this field) and DNI.The proccess is more fluid and simply for this kind of people.
When the work day finish, I will export to CSV all the notes. Then, this CSV will be imported to our sql server system.
Regarding Rasperry Pi, I dont remeber if a mentioned it, but I need to remove the routers of our network in the near future. We will use only AP (we will have a Sophos UTM firewall).
So, When I have this topology working well, I will configure moodle in a central server and the netbooks will be connected through AP´s which the vlan will has not internet enabled.