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Cisco IOS Cookbook, 2nd Edition by Ian Brown, Kevin Dooley

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Using Time-Based Access-Lists

Problem

You want to filter application data based on the time of day.

Solution

To filter application data based on the time of day, use the following commands:

Router1#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#time-range NOSURF
Router1(config-time-range)# periodic weekdays 9:00 to 17:00
Router1(config-time-range)#exit
Router1(config)#ip access-list extended NOSURFING
Router1(config-ext-nacl)# deny   tcp any any eq www time-range NOSURF
Router1(config-ext-nacl)# permit ip any any
Router1(config-ext-nacl)#exit
Router1(config)#interface FastEthernet0/1
Router1(config-if)#ip access-group NOSURFING in 
Router1(config-if)#end
Router1#

Tip

This feature relies on an accurate system clock to function properly. It is highly recommended that you use NTP to synchronize the router’s clock. See Chapter 14 for more information regarding NTP.

Discussion

Timed-based access-lists allow you to filter application data based on the time of day. In our example, we’ve built an access-list that denies HTTP traffic during the work hours, Monday to Friday, from 9:00 to 17:00. Timed-based access-lists also allows control over other router features, based on the time of day, such as policy-based routing, CAR statements, ACL logging, on-demand link activation, or security policies, to name a few.

To configure a timed-based access-list, you must first configure a time-range:

Router2#configure terminal Enter configuration commands, one per ...

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