Setting the default route on Solaris is easy. If you are trying to just set the route temporarily you can use the route command:
route add default <ipaddress>
route add default 192.168.1.1
If you want the route to be persisted when you reboot the system, you will need to set the route in the /etc/defaultrouter file.
echo 192.168.1.1 > /etc/defaultrouter
Note that Solaris 10 includes “zones” that can also configure this same behavior. There will be more articles covering this in the future.