Cisco Catalyst 2960 Software Configuration Manual page 727

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Configuring Network Security with ACLs

Configuring IPv4 ACLs

Switch(config-ext-nacl)# no permit ip host 10.1.1.3 any

Being able to selectively remove lines from a named ACL is one reason you might use named ACLs

instead of numbered ACLs.

After creating a named ACL, you can apply it to interfaces (see the

"Applying an IPv4 ACL to an

Interface" section on page

Using Time Ranges with ACLs

You can selectively apply extended ACLs based on the time of day and the week by using the time-range

global configuration command. First, define a time-range name and set the times and the dates or the

days of the week in the time range. Then enter the time-range name when applying an ACL to set

restrictions to the access list. You can use the time range to define when the permit or deny statements

in the ACL are in effect, for example, during a specified time period or on specified days of the week.

The time-range keyword and argument are referenced in the named and numbered extended ACL task

tables in the previous sections, the

"Creating Standard and Extended IPv4 ACLs" section on page

"Creating Named Standard and Extended ACLs" section on page

Time-based access lists trigger CPU activity because the new configuration of the access list must be

merged with other features and the combined configuration loaded into the TCAM. For this reason, you

should be careful not to have several access lists configured to take affect in close succession (within a

small number of minutes of each other.)

The time range relies on the switch system clock; therefore, you need a reliable clock source. We

recommend that you use Network Time Protocol (NTP) to synchronize the switch clock. For more

information, see the

"Managing the System Time and Date" section on page

Catalyst 2960 and 2960-S Switches Software Configuration Guide, Release 15.0(1)SE

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