conf t
interface GigabitEthernet0/2
 ip access-group in_block in
exit
!
ip access-list extended in_block
 deny   udp any any eq ntp log
 permit udp host 91.1.1.1 host 91.1.1.3 eq domain
 permit udp host 91.1.1.1 host 91.1.1.13 eq domain
 permit tcp host 91.1.1.1 any
 permit icmp host 91.1.1.1 any
!