Andy Hewat posted the route:
The Munda Biddi is a purpose built mountain bike trail currently stretching from Mundaring to Manjimup south of Perth in Western Australia. The trail is planned to continue all the way to Albany paralleling the famous Bibbulmun walking track. Current length is listed around 600km but that includes some redundant out-and-back sections into nearby trail towns. While a dedicated mtb track the Munda Biddi is also open to foot traffic.