External login

Hi,
I want know if exists a method for external login.
I read the manual of mikrotik, I know replace the login.html for that it can redirect to an external login, but the external login must submit to action login of the mikrotik. Mikrotik need this submit because it extract the IP Address of the header request.

Can mikrotik take IP Address of the parameters request?

Thanks.

PD: Sorry, my english is not good.