Turns on SSG's ability to act as a generic RADIUS proxy for client devices, such as a GGSN, that aren't themselves SSG-aware. Enabling this lets SSG sit transparently between a non-SSG client and the real AAA server so mobile-data sessions still get SSG's subscriber-management treatment even though the client was never built to talk to SSG directly. A wireless carrier terminating GGSN sessions on a router running SSG would enable cssgCfgRadiusProxyEnabled so PDP-context Access-Requests from the GGSN get proxied through SSG for service selection before reaching the carrier's AAA server.