Rule Numbering; Implementing Time-Based Acl Rules; Fragments Filtering With Acls - HP 5830 Series Configuration Manual

In addition, add a rule range remark to indicate the start or end of a range of rules created for the same
purpose.

Rule numbering

ACL rules can be manually numbered or automatically numbered. This section describes how automatic
ACL rule numbering works.
Rule numbering step
If you do not assign an ID to the rule you are creating, the system automatically assigns it a rule ID. The
rule numbering step sets the increment by which the system automatically numbers rules. For example, the
default ACL rule numbering step is 5. If you do not assign IDs to rules you are creating, they are
automatically 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 is numbered 15. If the ACL does not contain any rules, the first rule is
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 only takes effect 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.
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Absolute time range—Represents only a period of time and does not recur.
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You can specify a time range in ACL rules before or after you create it. However, the rules using the time
range take effect only after you define the time range.

Fragments filtering with ACLs

Traditional packet filtering matches only first fragments of packets, and allows all subsequent non-first
fragments to pass through. Attackers can fabricate non-first fragments to attack networks.
To avoid the risks, the HP ACL implementation does the following:
Filters all fragments by default, including non-first fragments.
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Allows for matching criteria modification, for example, filters only non-first fragments.
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