Rob noticed, that in an experiment with gated running, the trafgen
would startup before gated got its routes.  The result was that trafgen
traffic would use the default route sending data out the control net IF.
When the real route came online, traffic would start going out the
proper interface but the source addr would still be the control net addr
so TCP ACKs would still come back via the control net.

By binding the local address for trafgen to 192.168.X.X we force the
source addr to be correct always.