Because the /etc/defaultrouter file is deprecated in Oracle Solaris 11, you can no longer manage routes (default or otherwise) by using this file. Instead, use the route command to manually manipulate the network routing tables. The route command manipulates routes for the active profile only. The default route, as well as all other routes, could potentially be replaced if the active profile changes. This issue is of no concern if you do not switch profiles on your system.
For more information, see Creating Persistent (Static) Routes.