PPPoE security issue.

Hi.

The Mikrotik manual section relating to the setting up of PPPoE servers states:

Security issue: do not assign an IP address to the interface you will be receiving the PPPoE requests on.”

Can someone please:

A. Explain the security issue, and/or

B. Tell me how, if I don’t assign an IP address to the wlan interface through which I - and Webmin - access the router and the network beyond it, I can administer both as I don’t want this Intranet traffic to pass over the PPPoE link (which might not even be established if there is a problem with the PPPoE server config. or the RADIUS server beyond) and thus be accounted as my Internet use.