Repeated Internet Connection Timeouts

I am currently experiencing periodic internet connectivity timeout issues which only began early this January. 

For a number of years I’ve been running my xFinity modem/gateway in Bridge Mode connected to my router without any issues.  But now all of my LAN clients, WiFi or ethernet connected, have their internet connections timeout when the issue occurs.  Local LAN connections are not impacted.  Note, exchanging the router for a different one doesn’t resolve the issue. 

Strangely, if I attempt to ping an external internet address while the issue occurs every other ping times out.

ping -t apple.com

Reply from 17.253.144.10: bytes=32 time=16ms TTL=55

Request timed out.

Reply from 17.253.144.10: bytes=32 time=18ms TTL=55

Request timed out.

Reply from 17.253.144.10: bytes=32 time=17ms TTL=55

Request timed out.

…this continues from a few minutes to a few hours or can be temporarily fixed by manually disconnecting and reconnecting the ethernet cable connecting router to xFinity modem/gateway.

Rebooting either the router or modem also temporarily fixes the issue.