6.10.4 ReadyNas and Nighthawk Link Aggregation error

You need to use LACP on the ReadyNAS, since that is the only aggregation mode that the router supports.  So no round-robin and no XOR.

Transmit Load Balancing and Adaptive Load Balancing aren't true aggregation modes - they are ways to use two NICS that are still independent.  So if you want to use them, you wouldn't configure aggregation on the router at all.

Also, the NAS needs to be directly connected to the router (no intermediate switches).  I believe the 8500 doesn't support jumbo frames, so you also need to make sure the NAS has the MTU set to 1500 (or match whatever is set in the router).

FWIW, in most cases there is little or no performance gain with bonding.  The RN104 is limited by it's CPU speed and RAM, and isn't really capable of saturating a single ethernet connection.

Also, LACP won't allow a single dataflow to exceed 1 gigabit anyway.  So if you are using LACP, you still can't see speeds over 1 gigabit with a single client. 

With just a few clients, you might see total speeds over 1 gigabit per second [or not].  The NAS and the router will map each dataflow they are sending to a single NIC using the mac address and IP address (since you are using layer 2+3).  So with two clients, the odds of the two dataflows leaving the NAS using different NICS are only 50-50 - and the same odds apply to dataflows leaving the router.  So the odds of using both NICS in both directions is only 25%.

So my advice to most home users is not to spend a lot of energy getting bonding to work, as it generally isn't worth the trouble.  That's particularly true with the RN104.

If you have a lot of clients, then link aggregation comes into its own, as the load on each NIC will tend to roughly balance as the number of simultaneous clients accessing the NAS grows.  That's a more likely scenario for a business network.