So we have 2 Xbox 360 Slims sitting side-by-side, they both connect to the same gigabit router (wndr3700) via cat6 cable. Both Xbox have the same network settings (auto, wired). Xbox #2 has no problems connecting to live, playing games, or staying connected. Xbox #1 randomly disconnects from live but only when playing a game, and it doesn't matter if the game is online or offline. Test network settings never produces an error code on Xbox #1. After I start playing a game I get disconnected usually within about 5 minutes. Once I quit the game and return to the dashboard I'm immediately signed back in to Live.
Xbox #2 never loses connection.
Xbox #1 experiences this problem both when Xbox #2 is on and being played and when Xbox #2 is turned off.
I've tried hard coding the IP address for Xbox #1 and placing it in my router's DMZ, but the random disconnects occurred at the same frequency.
I also tried setting up port forwarding (using the ports recommended in the Xbox 360 troubleshooting documents) to the Xbox #1 IP address, this also did not affect the disconnects.
The NAT setting on my router is Open.
UPnP is enabled.
Internet connection type is Cable - Comcast
Previously we were using a DLink Dir-655 and did not see this problem. The problem started when we switched to Netgear WNDR3700.
Any ideas why this is occurring and how to fix it?