My speedlight SB-600 would not trigger my D300S further then about 2 meters (6ft) In contrast my D200 trigger the speedlight at least 5-meters from the source.
1.) Any idea where the sensor of the SB600 is located?
2.) Is there a solution to this? I would like to use my D300 from about 4 meters from the source.

Sensor is just forward of your battery door and is about 10mm in circumference.
It also has a symbol above it. That Symbol looks a lot like the symbol for Commander mode in the SB600 menu.

The solution for outdoor is to have line of sight with the On-board flash And the SB600 sensor seeing each other. It can be hit or miss. But my experience with Nikon CLS has been good out of doors. Indoors you can get away with a lot more due to signal bounce.

Originally Posted by angevin1 Sensor is just forward of your battery door and is about 10mm in circumference. It also has a symbol above it. That Symbol looks a lot like the symbol for Commander mode in the SB600 menu. The solution for outdoor is to have line of sight with the On-board flash And the SB600 sensor seeing each other. It can be hit or miss. But my experience with Nikon CLS has been good out of doors. Indoors you can get away with a lot more due to signal bounce.

I am delighted with this information. After more experimentation I found that my lens is the culprit and not the camera. I presume the lens body may shadow a crucial bit of light. I will check this out later today. I think we are about 7 or 8 hours before you. I am always trying to keep a line of sight and some times I am surprised at the angles it fires. With my 500mm lens however, it is not that easy.
Aart