4
numbered 0, 5, 10, 15, and so on. The wider the numbering step, the more rules you can insert between
two rules.
By introducing a gap between rules rather than contiguously numbering rules, you have the flexibility of
inserting rules in an ACL. This feature is important for a config order ACL, where ACL rules are matched
in ascending order of rule ID.
Automatic rule numbering and renumbering
The ID automatically assigned to an ACL rule takes the nearest higher multiple of the numbering step to
the current highest rule ID, starting with 0.
For example, if the numbering step is 5 (the default), and there are five ACL rules numbered 0, 5, 9, 10,
and 12, the newly defined rule will be numbered 15. If the ACL does not contain any rule, the first rule will
be numbered 0.
Whenever the step changes, the rules are renumbered, starting from 0. For example, if there are five rules
numbered 5, 10, 13, 15, and 20, changing the step from 5 to 2 causes the rules to be renumbered 0, 2,
4, 6 and 8.
Implementing time-based ACL rules
You can implement ACL rules based on the time of day by applying a time range to them. A time-based
ACL rule takes effect only in any time periods specified by the time range.
The following basic types of time range are available:
•
Periodic time range—Recurs periodically on a day or days of the week.
•
Absolute time range—Represents only a period of time and does not recur.
You may apply a time range to ACL rules before or after you create it. However, the rules using the time
range can take effect only after you define the time range.
IPv4 fragment filtering with ACLs
By default, an ACL packet filter on the switch matches all fragments to prevent attackers from fabricating
fragments. To improve efficiency, you can configure the
fragment
keyword to apply an IPv4 ACL rule only
to non-first fragments.
ACL configuration task list
Complete the following tasks to configure an ACL:
Task Remarks
Optional
Configuring an IPv4 advanced ACL
Configuring an IPv6 advanced ACL
Configuring an Ethernet frame header ACL
Required
Configure at least one task.
Optional