If you can't ping the other devices from each other, you've definitely got a "network problem" as the Denon puts it.
What type of problem would that suggest, or what possible route of correction? I now have two routers in series and I can ping either of the routers from the computers but no computer can ping any of the other computers.
If you put a router after the att modem, you'd want to put all of your devices behind it so as to keep them on the same network. Part of the issue is that the att modem is already doing NAT (translating your outside ip address into multiple inside ip addresses) and because it's pretty generic to use 192.168.1.x, your existing router probably also uses that. It's a no-no to use the same network on both sides of the router, so that would undoubtedly break everything.
Set things up this way, i.e., denon/computers-->netgear rp614v1 router-->att 2701hg-b gateway-->internet, and everything connects flawlessly with the exception of the Denon. Went onto the internet and upgraded the netgear router's firmware, ironically that now includes a UPnP button for me to leave unchecked.
The Netgear router can also see the Denon and lists this as an "attached device," however I have tried to set the Denon up as a DMZ computer which Peter suggested trying yet so far has not helped and for some reason after doing this and then reverting back to normal DHCP, it takes either router a while to notice the Denon again, so I'm in wait mode at the moment, not that I have a lot more tests I can think of. Actually when the Denon reappears I still have to try connecting with the correct values input for the new network, in which the default gateway value appears to be given by the netgear router (its LAN address) whereas the primary DNS value is given by the att cable/modem router (its LAN address), based on the "ipconfig" info given up by the computers, still I'm not holding my breath.
One thing: The MAC address listed on the back of the Denon is not the same as the MAC address that shows up in the router's device list, whereas the MAC addresses listed in each computer's "ipconfig /all" info is the same as the MAC addresses of the computers listed in the router device list . Not sure what this indicates, perhaps it provides a clue as to what is going wrong?
Finally there are a few threads on Google that suggest Netgear routers may not work/play well with the 3808, I could go out and buy a DLink but anticipate I will hold off until I have more info, e.g., some reason to believe that the router is the root, proximal, or distal cause of the problem.
