Serious music question?

Okay, I was trying to do ear training (on relative pitches). And i realized that i can identify the pitches when it is from the tonic to somewhere up to an octave above it right? But i have difficulty when it is below the tonic, or more than one octave above the tonic. And i went on http://www.musictheory.net/exercises/ear-interval to learn this. There I saw that they only had the tonic and everything up to the octave above it. Is that all i really need to know and is there a concept behind finding the relative quality of the notes outside of that one octave? Thanks people (: