i'm away from my home so can't check...if i recall correctly..i used CIFS (or was it FSTAB) and entered the login details for the Asus router..i.e. admin and the password you set up..and then it works...as i said earlier you need to do this for each folder you want to mount...so if you have a video, music, photos folder on the drive conneted to Asus..u can create 3 mounts one for each folder..and then it shows in your STB ....
Hope that helps..let me know if it doesn't and i'll try to check on my box tomorrow or day after...