Pagination , Routing 404 - Newbie

$route ['posts/(:any)' ] = 'posts/view/$1' ;
This route find single post. In your pagination, '/post/{page}' will find post using page param not navigate to other pages and I'm sure in your Post controller searching for invalid post will show 404 page. Btw at the bottom of route, $route ['(:any)' ] = 'pages/view/$1' ; also for viewing single post.

Keep calm.