In the manual it says to turn on slaves before primary controllers, but that doesn't apply to two controllers, a primary and a secondary. When you connect via the RJ45 expansion ports (OUT to IN) you have to power up the primary first, wait for its status light to come on and then power up the secondary. Then the link light comes on but no trace of the connection in the SmartWindow application. Hmmm.
The Debug Console, which is supposed to show it just comes up blank, with a blank dropdown menu. My guess is that it doesn't work correctly in Windows XP.
Maybe it doesn't matter. If one port of the Spirent 600 can spew out 1GB of data flat out then that should be enough to saturate a 1GB port on any router.