Time-Based Access Lists

Until recently, an access list was either implemented or not. An administrator would have to change the configuration to include a feature, such as blocking Internet access, and then would have to physically remove either the ACL or the access-group statement to allow access. This wasn’t convenient if the goal was to block employee access during work hours, but to allow access at other times of the day.

Since version 12.0 of the IOS, it’s possible to create access lists that can incorporate date- and time-sensitive features. This allows filtering to occur only during certain hours of the day or on certain days of the week. IP and IPX extended access lists are currently the only functions that can use time ranges. Time ranges enable the network administrator to specify when the permit or deny statements in the access list are in effect. Both named or numbered access lists can use the time range feature.

Two separate tasks are required to implement time ranges:

• Define a time range.

• Reference the time range.