M9 Plus in AP mode - WiFi clients of slave Deco sometimes lose DHCP
This is a new (2-day old) installation of two Deco M9 Plus, in AP mode behind a home router. Both Decos are updated to 1.2.8 Build 20190403 Rel. 43515, and I'm using the iOS app version 1.8.6. The Decos say "V1.2" on the bottom labels.
The symptom I'm seeing is that sometimes a Windows laptop will show connected to WiFi with no internet access. The problem also happens to other WiFi devices including TP-Link HS110 smart plug, which will become unavailable through Kasa while still showing a solid internet connection on the device status light. So far the problem seems to happen only when the slave Deco is connected.
The laptop problem occurs when waking from sleep, or can be triggered by turning its wireless off and back on. This Win7 laptop with Intel(R) WiFi Link 5100 AGN is known-good and has been working with my previous WiFi setup without problems. When the problem occurs, the laptop shows connected to the SSID but has a link local IP address, not a DHCP one on the LAN. When the problem occurs, both Decos show green LED lights and good health status in the Deco app. During the probem, other WiFi and wired clients of either Deco are functioning normally and can communicate with each other.
During the problem, packet capture on the laptop shows it receiving broadcast traffic (MDNS, ARP, TIPC, etc.). If I then use the app to reboot the slave Deco (or remove power from it), the laptop will immediately broadcast DHCP dicover and successfully join the LAN while the slave Deco is rebooting. The laptop will then continue to work until sleep/wake, or until the Wifi connection is manually disconnected and reconnected.
If the slave Deco is powered off, the laptop will work normally across sleep cycles when reconnecting to the master Deco. All testing has been done with the laptop in and Decos in fixed positions.
So it looks to me like intermittently DHCP is not propagating to WiFi clients of the slave Deco. I have not yet seen this problem with wired clients of the slave Deco. I have not seen this problem with clients of the master Deco. During the problem with either the laptop or an HS110, other clients of both Decos are behaving normally. Again, during the problem both Decos show green LED and "healthy" status. During the problem, turning off the slave Deco will allow WiFi clients to automatically and successfully connect to the main Deco.
Any help would be appreciated. Please let me know if I can gather any other useful troubleshooting information.