sql nas and accounting

Two questions: 1. Does listing clients in the nas database table support virtual servers? If so, what field do I enter that info in and do I need to update the SQL query used in dialup.conf? 2. How do I get sql accounting to work? That is, how do configure freeradius to update the radacct table? Right now, freeradius process seems to be rejecting accounting requests: "Ignoring request to accounting address * port 1813 from unknown client..." The"unknown client" works fine for authentication. Thanks for any tips.