Followed the directions at https://www.xfinity.com/support/articles/set-up-parental-controls-with-comcast-networking to use 10.0.0.1 with my to block specific websites through my Gateway modem/router (PN: TG02DCW3482P2).
Failure 1: Directions fail to mention that to activate any new block requires power cycling the router
Failure 2: Will not block https://www.youtube.com no matter what I tried.
Failure 3: Cannot block any website on a schedule
Failure 4: Can block websites if set to "Always" block, but one can override these blocks by creating multiple browser tabs all trying to access the sites. Enough simultaneous requests appears to overwhelm the block. Once that block is bypass the browser somehow retains a memory of this bypass even if you close the browser and reopen. To erase that memory in Firefox have to Clear all HIstory twice before closing Firefox.
What does work. Xfi Webapp seems to do a reliable job with Bedtime Scheduling for each profile, and Pause/Unpause commands. But more sophisticated control through 10.0.0.1 is crippled. Please fix this and hire some teenagers to try to bypass your controls before rolling it out.