Here is my network setup...
HTPC -> DDWRT -> Rosewill easyN4 -> DDWRT -> XBOX
The DDWRT routers are client bridges, and the rosewill is the primary. I also have a wireless laptop that can access both DDWRT routers.
Here's what works.
Everything has internet access.
I can access both dd-wrt and primary from laptop
I can remote desktop to HTPC
XBOX downloaded updates via LIVE, lots of them, hasn't ever been online.
XBOX shows the connection screen and gives a code, 8 digits
WMC is able to check the code, if i put it in wrong, it tells me.
It won't go any further than this.
A couple things I've noticed:
If I ping the xbox - I get replies from a different IP. xbox is .100, replies from .102
The Windows Media Extender service will not stay enabled, always reverts to disabled, I don't know if Media center controls this during setup, but it won't stay on. I've followed a number of other ideas I found on the web, like various services, turning off ICS. Under media streaming I cannot allow the xbox to stream because it doesn't show up. In my network map, xbox is not there.
Ok that's all the info I think I can give on this, does anyone have any ideas for what to try next?