Most ISP's will automatically assign the correct permanent IP for the user login -Telstra BPD doesn't for some reason. You need to set this using the guideline below which was taken from the faq on the corporate site a while ago.
the tiip is the telstra modem you are dialing into
the custip is the ip your modem will use that needs to be set below
your lannet is the range of routable addresses that you can use on your local net, of which you only need one, which you will assign the the e-smith server.
"If your ISP is not able to configure their Remote Access Server (RAS) so that it allocates the correct IP address, then follow the intructions below to create a custom template. With this template in place there is no need to set the remote IP address and subnet mask. We also recommend you do NOT specify external primary and secondary DNS servers.
# Make a copy in the custom area of the template fragment you
# need to change
mkdir -p /etc/e-smith/templates-custom/etc/diald.conf
cp /etc/e-smith/templates/etc/diald.conf/pppd-options
/etc/e-smith/templates-custom/etc/diald.conf/pppd-options
# Edit in place the new template fragment
perl -pi -e "s/noipdefault/x.x.x.x:y.y.y.y/"
/etc/e-smith/templates-custom/etc/diald.conf/pppd-options
# Here x.x.x.x refers to your custip IP address, y.y.y.y refers to
# the ISP RAS's IP address, the tiip. You *should* be able to leave y.y.y.y blank
# Expand the templated configuration file (/etc/diald.conf) and
# restart diald.
/sbin/e-smith/signal-event console-save
"