27-16
Catalyst 3560 Switch Software Configuration Guide
78-16156-01
Chapter 27 Configuring Network Security with ACLs
Configuring IP ACLs
Using Time Ranges with ACLs
You can selectively apply extended ACLs based on the time of day and 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 IP ACLs” section on page 27-7
, and
the
“Creating Named Standard and Extended ACLs” section on page 27-14
.
These are some of the many possible benefits of using time ranges:
•
You have more control over permitting or denying a user access to resources, such as an application
(identified by an IP address/mask pair and a port number).
•
You can control logging messages. ACL entries can be set to log traffic only at certain times of the
day. Therefore, you can simply deny access without needing to analyze many logs generated during
peak hours.
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.)
Note
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 6-1
.
Beginning in privileged EXEC mode, follow these steps to configure an time-range parameter for an
ACL:
Repeat the steps if you have multiple items that you want in effect at different times.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
time-range time-range-name
Assign a meaningful name (for example, workhours) to the time range to
be created, and enter time-range configuration mode. The name cannot
contain a space or quotation mark and must begin with a letter.
Step 3
absolute [start time date]
[end time date]
or
periodic day-of-the-week hh:mm to
[day-of-the-week] hh:mm
or
periodic {weekdays | weekend | daily}
hh:mm to hh:mm
Specify when the function it will be applied to is operational.
•
You can use only one absolute statement in the time range. If you
configure more than one absolute statement, only the one configured
last is executed.
•
You can enter multiple periodic statements. For example, you could
configure different hours for weekdays and weekends.
Refer to the example configurations.
Step 4
end
Return to privileged EXEC mode.
Step 5
show time-range
Verify the time-range configuration.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
