I am trying to use ACL to block a range of public IP's entering a 2960 switch everything else should not be effected   interface gigabitethernet1/0/1 ip access-group 1 in   access-list 1 deny x.x.x.0 0.0.0.255   why doesn't this work

I use a 877VA for my VDSL connection How can I sync its clock to an external NTP time server without the modem itself replying to NTP queries from external users. I need it to sync but don't wan it open to NTP amplification attacks