PC slow to make connection through gateway after network address change

[Dave_61]

Model C6220

Firmware V1.02.11

Windows 10 home 19041.630

Chrome browser

I wanted to add access points to my WiFi network. I reset my router to factory defaults as I was using an non-standard address for my LAN. Since resetting, I often cannot connect to my router to configure it. At the same time, I cannot ping my DNS servers assigned by my ISP (Comcast). I can get to most of my ISP websites, run a speedtest app (via google) but not open a link to a speed test website, I guess because my ISP websites don't need a DNS for me to access them. Most other websites are not accessible at the same time.

After a period of time, everything will fix itself and work fine with no action taken by me. I can surf seemlessly, ping DNS servers successfully and use the web interface to configure my router.

[FURRYe38]

What non standard address were you using on the LAN side? 

How is the LAN side IP addressing configured now? 

Did you power OFF ALL devices then back ON after resetting the modem and setting it up again? 

What additional APs did you add? 

[gburns53]

nm

[Dave_61]

Original LAN network was 10.XXX.XXX.0, subnet 255.255.255.0. I switched the router to more standard 192.168.0.254 in order to configure access points (reused old router hardware, just not as a router).

AP's are not connected now because of the issues I was having, but they were an old Cisco WiFI Router and an old Netgear WiFi router. Again, they were not being used as routers, simply as WiFi AP. DHCP was turned off on each, and address was set to 192.168.0.253 & 253. They were connected to Cisco 1G switch which is also connected to C6220.

Right now, with only the C6220 and nothing else connected, everything appears fine, although if I reboot a PC or laptop (both WiFi), I go through a period where the problem re-occurs, i.e. some websites available, unable to connect to C6220 for configuration, cannot ping DNS servers. Hour or two later, everything works fine.