Microsoft Windows [Version 6.0.6001] (C) Copyright 2006 Microsoft Corp. c:\windows>netsh ras diagnostics set modemtracing ?
set modemtracing [ state = ] ENABLED|DISABLED
Enables or disables tracing of modem settings and messages during a network connection.
state - tracing state of modem
ENABLED - Enables modem tracing for all network connections that use a modem.
DISABLED - Disables modem tracing for all network connections that use a modem.