Need help with settings - extending wifi
So I need some networking help. I have xfinity for my internet with an arris tg1682g modem/router. However, it's located in a horrible spot. So I ran Ethernet to a central point and plugged in an AirPort Extreme (Newest version). From the extreme, I ran Ethernet to the basement, and plugged in a first gen express. i also have a second gen express located in the upstairs bedrooms.
the extreme and the expresses are set to extend the network, however the signal keeps dropping or being slowed dramatically even when you are inches away. when I had the arris in bridge mode and used the extreme to create the network and the expresses to extend everything worked exceptionally well. However, we had xfinity home security installed, and they took the arris out of bridge mode because they wouldn't allow me to use the extreme for the security system. Since then I have had nothing but problems with my internet. It either drops off significantly in performance (150mbps down to 18mbps).
I also get error messages that the network cannot be found on the two Ethernet connected airport devices.
It has been very frustrating because the Comcast IT people are horrible. So any help would be greatly appreciated. Thanks in advance.
AirPort Extreme 802.11n (4th Gen), OS X Yosemite (10.10.5), iPad air 2 running iOS 9
