I am having recent periodic problems with my wifi which consists of ATT Fiber w/BGW-210 in ip passthrough mode and TP-Link S4.  I have had the BGW210 for 2 years without problem…maybe a single outage of a few minutes…very reliable.  In February this year, I changed the setup on the BGW210 to ip passthrough and added a TP-Link Deco S4 2-node mesh router to manage the ATT 300 plan.  My goal was to improve the ring camera on our patio which periodically lost connection.  The upgrade has significantly improved the camera connection and there is good connection everywhere in our 3000 sqft home and patio.  

BGW210 passthrough settings: 
Allocation mode: Passthrough
Passthrough Mode: DHCPS-fixed
Set Passthrough Fixed MAC Address: to main Deco address
Passthrough DHCP: 7 days
Manually shut off all Wi-Fi
Firewall Advanced: everything turned off.

All worked great for a few weeks and then something started happening. Four times the wifi stopped working which means the BGW210 appeared to be working (speedtest was good) but might have had a short outage but the Decos were not reachable, displayed a red light and all wifi stopped.  It was if there was a short BGW210 outage which the ATT gateway resolved and the Deco did not resolve, reset or reboot.  A manual Deco restart was required to resolve.  The first time it happened there was an ATT truck installing fiber at a neighbor’s house so I thought incidental.  Last night I was at a Guardians-Braves game and my wife had no internet or TV…definitely not a coincidence or acceptable. We have quite a bit of automation and this is too unreliable.  If I cannot find an answer, I will revert back to the ATT gateway.

The only thing that I see is the BGW210 logs show “Invalid IP Packet” errors from both 192.168.1.254 and 192.168.254.254.  

Does anyone have any thoughts of how to triage or resolve?

Thanks…