I have had this problem for a long time now, it would seem, but I only really noticed it after the release of SSB 3DS. While both my 3DS and Wii U connect without fault to the internet, with no issues using the eShop, Miiverse, or even joining lobbies in online games. The problem is;I can't join any games. I have forwarded all ports that the 3DS and Wii U are able to use, put the in the DMZ, disabled my firewall, tried all available protocols in my router, but still nothing. At first I thought it was a bug, especially since I saw so many posts about it around launch, as well as a forum post claiming Nintendo support had told the poster they re working on a fix, yet the problem persists. The error message I'm getting varies slightly, but are always in the same range of errors. The one I just got was Error Code: 118-0514. So, having had this problem for such a long time, I have been able to investigate quite thoroughly. My router is a D-link DIR-645, so it is by no means old or outdated. My download speed averages at 30Mb/s, and my upload speed averages 5Mb/s, so I don't have a slow connection, and my latency is pretty low. As previously mentioned, I have been able to rule out both ports and the firewall as the possible culprit, and yes, I manually assigned my Wii U and 3DS IP addresses, before putting them in the DMZ. It is not a problem caused by the consoles, as I have since switched to a New 3DS, inhibiting the same problem. I do not have this problem with PC games either. It could be a problem with my ISP, but that begs the question, why was it so widespread when the game first launched? What makes this even stranger, is the fact that it sometimes DOES let me join an online game, after multiple failed attempts. In Kid Icarus Uprising, I had about a 15% success rate in joining a match. In SSB 3DS, it never lets me join a friends match, or for fun, but about 5% of the time, I get to play a match in 1v1 for glory. It is exactly the same in SSB Wii U. I can not play online at all in Mario Kart 8, although it lets me upload and download ghosts for time trials. In Wind Waker HD I have no problems with the Miiverse integration, either. I can also play Pokemon Y completely without any problems. I also don't have any problems playing games online on my laptop over the wireless network, although I have had problems with the audio cutting out in Skype, but I haven't been able to consistently reproduce this problem on my laptop, or at all on other wireless devices, such as my phone, or other laptops. I am also the only person, and the administrator of the wireless network, so I have full control over environmental factors. If I share my connection from my phone, and connect to that, the problems go away. I find it very strange how inconsistent these problems are. What also strikes me as odd, is how common it seemed at first, but as mentions of it quickly faded away, the problem remained the same. Has anyone dealt with these problems? It is clear that it has something to do with my network, but no matter what, I just can't figure it out.