D6300 and old wireless DSL modems as repeaters

I thought I should share my experiences of trying to configure a D6300 modem as the base and a couple of older DSL modems as repeaters. My original post: http://forum1.netgear.com/showthread.php?t=85934 explains what I tried to do, and on testing a second wireless N600 router as a repeater I realise now that the D6300 will only work with another D6300. The following combinations of DSL wireless modems I have tried:

D6300 base + DGND3700 repeater: they connect to each other but no Internet acress when connected to the repeater.

D6300 base + N600 repeater: they connect to each other but no Internet acress when connected to the repeater

D6300 base + D6300 repeater: Success! Internet on both sides.

N600 base + DGND3700 repeater: Success! Internet on both sides.

Conclusion: Unless there is a secret option to enable the D6300 to play nice with older wireless routers as repeaters then it seems it just won't work.