Suggest change the channel of your router's 5G

As far as I know, one tunnel goes to one client server , not two

My VR600 works fine since I bought it last month Who is your ISP? Is DSL light solid on the router ? any special settings on the old router? Better double check the connection type, VPI, VCI ,...

http://forum.tp-link.com/showthread.php?101005-TL-WR841N-Guest-Network-no-DHCP

what's the firmware version and hardware version on your router? Update to the latest firmware first

How about the lights on the WPA8730 when you lose connection? How often it will happen? they are powerline products , will affected by electrical environment. Better to put them in the same room to...