Eureka! Peter you nailed it! I began to scroll the above mentioned thread, voluminous, mostly chaff at first and nothing related to routers and then my eye picked up a comment regarding make sure you plug into the ethernet port and not the denon link jack. So I rushed over to check and lo and behold not only had a missed the correct port after scanning the diagram and reaching behind the entertainment center, but I had plugged into the wrong box, I had plugged into the Sony 350, hence the incorrect MAC address! For some reason I had failed to reverse the image of the diagram properly in my mind so when I looked in the back of the rack I was looking for an ethernet port on the left rather than the right, so the Sony looked good.
Plugged the ethernet cord into the correct jack and seconds later I was listening to German internet radio (I guess that's one of the most popular for some reason) through the power line network directly into the att combo/router. What a bonehead mistake,
, for days I've been tracing all of the connections and learning everything I never wanted to know about networks, but never suspected I would have made such an elementary flub at the very beginning of the chain. That's one of the problems with getting old, you make mistakes you can't even begin to imagine you would be capable of so it's not immediately obvious where you need to doublecheck. Note to self: when trouble shooting, begin with a triple check of connectivity.
Thanks everyone for all of your help and patience, I learned a lot and perhaps some of the knowledge will be useful some other rainy day.
