The way I understand it is that when in bridged mode, the DAP-1522 is basically acting as an extension to the router. I have never run it in AP mode so I don't know how that works.
At least on my setup, all reserved ip's in my entire network are dictated by my DIR-655 router. My DAP has no role in assigning ip's.
Every device is set to obtain it's ip automatically, but the reservation list in my router dictates which ip that is.
My roommate's gear upstairs is all assigned a reserved ip by my router (he has a PS3 Fat 80GB and a HP laptop wired to the DAP-1522) (pan right to see his gear....the image came out too big.)
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Every device in my network technically has a DHCP assigned ip, but in practice, the ip's are all static because of the reserve list on the router.
Ignore the yellow/orange lines....those have to do with PS3 Media Server. I made this map as a reference for use over in those forums. No bearing on DHCP or the DAP-1522.