Why aren't all web sites blocked when I enable MAC or IP filtering on my Motorola cable modem router (MG7310, MG7315, MG7540, MG7550)?

ANSWER: When you enable  IP and/or MAC filtering,  you must also disable stateless DHCPv6.  This will block all web sites.

To do this,  go to  Advanced> Basic Router> DHCPv6

At the bottom of this page is the heading  - DHCPv6 More settings. Under this heading, set  Stateless DHCP to disabled and click Save.