A permanent static route for Macintosh OS X (10.4.7)

I have set up OpenVPN on our pribvate network, but our special setup requires manually adding a static entry to the routing table of computers that we want to access from the outside via our VPN server. In SuSE Linux this is a nobrainer as Yast provides a section where to add static routing information. On MacOS X the command line works, but upon reboot the route is lost:

route add

Check what the route is for a specific IP:

route get

The same command has a different syntax on Linux though:
route add -net netmask gw 192.16

In order to preserve the routing information over a reboot I created the folder AddRoutes in /Library/StartupItems. Inside this folder there have to be two files: AddRoutes and StartupParameters.plist . The content of these files is the following:

# Set up static routing tables
. /etc/rc.common
StartService ()
ConsoleMessage "Adding Static Routing Tables"
route add -net
StopService ()
return 0
RestartService ()
return 0
RunService "$1"

Description = "Add static routing tables";
Provides = ("AddRoutes");
Requires = ("Network");
OrderPreference = "None";

These files need to be readable and executable by everybody for MacOS X 10.4.7. However, MacOSX might wipe these files with each system upgrade (at least from Mountain Lion to Mavericks my settings disappeared completely). After recreating them, I got the error message "Insecure Startup Item disabled" at boot and I needed to give the directory and the files the following permissions to make the error to disappear:

drwxr-xr-x 4 root wheel 136 Aug 6 22:44 AddRoutes
-rwxr-xr-x 1 root wheel 238 Aug 6 22:43 AddRoutes
-rwxr-xr-x 1 root wheel 123 Aug 6 22:44 StartupParameters.plist

However, the route does not get added in Mavericks by this procedure and I could not find any information how to do this.

The original information is from the following website: http://macosx.com/forums/showthread.php?t=267209.