this will allow internet access for a particular time interval.
R4(config)#int f0/0
R4(config)#int f0/0
R4(config-if)#ip nat inside
R4(config-if)#int f0/1
R4(config-if)#ip nat outside
R4(config)#time-range testing
R4(config-time-range)#periodic daily 12:00 to 15:00
R4(config-time-range)#exit
R4(config)#access-list 110 permit ip any any time-range
testing
R4(config)#access-list 110 deny ip any any
R4(config)#ip nat pool test 179.100.0.2 179.100.0.2
netmask 255.255.255.252
R4(config)#ip nat inside source list 110 pool test overload
