BroadBand Choice can be used to find out which telephone exchange your phone is connected to.
Then look up the Australian Exchange Guide to find its address.

One not very accurate way is to get in your car and drive there. It may or my not give you a good number, because your phone wire may not take the same route.  Similarly for whereis’ directions.

Another way is to ask your ISP.  Telstra and the ISP know, but they may not always want to tell you due to rules and regulations within Telstra.

A third (very approximate) method is to divide the Loop Attenuation shown on the modem’s Status Page by 13.81.  E.g. 34dB attenuation indicates approx 2.5 km from exchange.

You can then look up this distance on Internode’s ADSL and ADSL2+ Speeds and Reach Compared chart to get an estimate of speed.

Note that this can be affected by a number of factors, such as …
– your phone line might actually be taking a more round-about route, and so could be further from the exchange.
– your phone line could be passing through a area with high interference, such as next to heavy machinery in an industrial area or close to a electricity transformer.

ISPs price ADSL2/2+ plans much the same as the 1.5Mbps ADSL1, and they don’t guarantee that your ADSL2/2+ speeds will be faster than 1.5Mbps.  The bottom line is that you’re only paying for 1.5Mbps and ANYthing over this should be considered a bonus.