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Time-based Access Control Lists (ACL)
are used to implement time-based Dial-on-Demand Routing (DDR). These
ACLs help control dialing when they are used to define what traffic
is interesting enough to cause or maintain a dial-up connection.
This mechanism can be useful to control undesired dialing that could
generate high charges by a telephone company. The definition of
interesting traffic is part of the DDR feature present in Cisco IOS®
Software. This feature is independent of the actual dial-up
technology being used (ISDN or plain old telephone service (POTS)).
The implementation of time-based
access lists requires two tasks. These are to define a time range
and then reference a time range. To define a time range, use the
commands shown in Figure
beginning in global configuration
mode. Repeat these tasks if you have multiple items you want in
effect at different times. For example, repeat the steps to include
multiple permit or
deny statements in an access list in effect at
different times.
In order for a time range to be
applied, you must reference it by name in a feature that can
implement time ranges. To reference the time range, create either an
IP extended access list or named access list (see Figure ).
After creating an access list, you must then reference it to make it
work.
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