I can access to one site by few different URLs

Hey, I've started learning codeigniter few weeks ago. I found one thing which is important to me, and I really don't know how to fix it.

I always pay attention to SEO, and i discovered that in Codeigniter often we can access to one site by few different URLs, like in this exapmle:

For this site: https://codeigniter.com/en/community

1. With adding index.php before the controller name -  https://codeigniter.com/index.php/en/community

2. When we've declared our route, users still can access by default path. I know user firstly need to know that, but it's still not good enough for me.

Do you know how can I handle this issues?