I have the Big Bundle: X1, XH, XI, and XTelephony
Xfinity Telephone/Internet Modem: Arris TG862 (disabled the WiFi; not bridging, four Ethernet 10/100/1000 ports active)
Xfinity Home Security Router: Netgear N150 (10/100)
Personal Home Router: Linksys WRT 1900AC (Using both WiFI bands, DHCP, and running gigabit ethernet out the back)
Problem: Xfinity Home Security install tech set up Netgear between Xfinity modem and my router resulting in speed drop off by 30-35 Mbps from prior tests (modem ports and Linksys router were hitting125-130Mbps. Attempts to switch router positions to recover bandwidth/speed loss caused XH problems (security cams lost video feed, monitoring devices connect failed, arming security system failed). Returned to routers connection original sequence and all XH functions returned along with slower speeds.
Solution from phone call with Xfinithy Wireless 2nd Level Tech:
1. Power off Arris, Netgear, Linksys.
2. Power on Arris and wait for solid status lights (again I had Xfinity disable WiFi on the Arris).
3. Connect Linksys internet port to Arris port #1 and power up.
4. Confirm PC connection to local network and Internet;
4a. Speed test shows improvement at 126-130Mbps!
5. Connect Netgear internet port to Modem port #2 and power up.
6. Confirm Netgear router status lights are green, wifi is blue and flashing.
7. Confirm XH security and monitoring tools/functions are working and online.
7a. Touchpad Control: Settings->Advanced Settings->Connectivity->Test Connectivity->Successful broadband and cellular connection to security servers is indicated by green dot/checkmark. Cameras had live video feed. Motion sensors were controlable. Alarm arm and disarm functions worked correctly. Alerts were registering. Thermostat was controlable.
7b. Remote control: Alarm arm and disarm functions worked correctly.
7c. PC on home network: Browser logged on to XH management portal successful. Confirmed all security functions, video camera feeds, and thermostat control worked correctly.
7d. Mobile App (wifi off, using carrier network): App logged on to XH management portal successful. Confirmed all security functions, video camera feeds, and thermostat control worked correctly.