Acl Rule Numbering; Implementing Time-Based Acl Rules; Filtering Ipv4 Fragments With Acls; Applying Acl - HP A6600 Configuration Manual

ACL rule numbering

If you do not assign an ID for the rule you are creating, the system automatically assigns it a rule ID.
Rule numbering step
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 numbered
0, 5, 10, 15, and so on. The wider the numbering step, the more rules 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 configuration 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 rule, 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

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 ranges 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.

Filtering IPv4 fragments with ACLs

Traditional packet filtering matches only first fragments of IPv4 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:
Filters all fragments by default, including non-first fragments.

Provides ACL-based firewalls with standard and exact match modes for matching ACLs that contain

advanced attributes, such as TCP/UDP port number and ICMP type. The standard match mode is the
default mode; it considers only Layer 3 attributes. Exact match considers all header attributes defined
in IPv4 ACL rules. For more information, see Security Configuration Guide.

Applying ACL

Use ACLs in QoS, firewall, routing, and other technologies for identifying traffic.
3