Eu peguei isso de um servidor 10.4 ...
/System/Library/LaunchDaemons/com.apple.ppp.l2tp.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>com.apple.ppp.l2tp</string>
<key>OnDemand</key>
<false/>
<key>Program</key>
<string>/usr/sbin/vpnd</string>
<key>ProgramArguments</key>
<array>
<string>vpnd</string>
<string>-x</string>
<string>-i</string>
<string>com.apple.ppp.l2tp</string>
</array>
<key>ServiceIPC</key>
<false/>
</dict>
</plist>