Helping my brother with this, he has a speco dsd8 DVR and can not view it unless he is on his wifi (or within his network) I have confirmed that the ports are open, port 80 5445 & 5446, we have also tried alternative ports. He uses an xfinity router/gateway but we have tried bridging this and just using a linksys router set up to see if it was xfinity's gateway blocking it. He has been fighting with this for months and even exchanged his dvr for a new one to see if that was the problem.
Any help will be much apperciated
-Steve