Hi;
I'm seeing the same problem last time, the guide above is really details, but one thing i miss out is that med500x doesn't support jumbo frame (since it is 100mbps only), hence your Disk Station need to ensure the network connection is 1000mbps with jumbo frame off.
Once i set this, the med can connect to the Disk Station.
On Med500x2,it is capable of 1000mbps, but still not support jumbo frame, you might want to check on that and set the DiskStation network connection properly.
hope this help.
wayne99