HP 6125G HP 6125G & 6125G/XG Blade Switches ACL and QoS Configuration - Page 9

ACL rule comments and rule range remarks You can add a comment about an ACL rule to make it easy to understand. The rule comment appears below the rule statement. You can also add a rule range remark to indicate the start or end of a range of rules created for the same purpose. A rule range remark always appears above the specified ACL rule. If the specified rule has not been created yet, the position of the comment in the ACL is as follows: • If the match order is config, the remark is inserted into the ACL in descending order of rule ID. • If the match order is auto, the remark is placed at the end of the ACL. After you create the rule, the remark appears above the rule. For more information about how to use rule range remarks, see the rule remark command in ACL and QoS Command Reference for your device. ACL rule numbering What is the ACL 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 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. 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: • Filters all fragments by default, including non-first fragments. • Allows for matching criteria modification, for example, filters non-first fragments only. ACL configuration task list 3