VG200 is stricly a voice gateway with basically voice
functionality. I don't believe aaa is supported.
please see links below for the right commands to use
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/multi_r/mrd_e.htm#1019117
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/multi_r/mrd_e.htm#1019156
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/multi_r/mrd_e.htm#1019470