Netgear XCM8806 Chassis User Manual - Page 319
ACL Evaluation Precedence, Rule Evaluation
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NETGEAR 8800 User Manual To delete a zone use the following command: delete access-list zone You must remove all applications from a zone before you can delete the zone. You cannot delete the default zones. ACL Evaluation Precedence This section describes the precedence for evaluation among ACL rules for the NETGEAR 8800 series switches. In many cases there will be more than one ACL rule entry for an interface. This section describes how multiple rule entries are evaluated. Multiple rule entries do consume hardware resources. If you find that your situation runs up against those limits, there are steps you can take to conserve resources by modifying the order of the ACL entries that you create. For details, see ACL Mechanisms on page 325. The section describes the following topics: • Rule Evaluation on page 319 • Precedence of Dynamic ACLs on page 320 • Precedence of L2/L3/L4 ACL Entries on page 320 • Precedence Among Interface Types on page 320 • Precedence with Egress ACLs on page 320 • Redundant Rules on page 320 Rule Evaluation When there are multiple rule entries applied to an interface, evaluation proceeds as follows: • A packet is compared to all the rule entry match conditions at the same time. • For each rule where the packet matches all the match conditions, the action and any action modifiers in the then statement are taken. If there are any actions or action modifiers that conflict (deny vs. permit, etc), only the one with higher precedence is taken. • If a packet matches no rule entries in the ACL, it is permitted. Often there will be a lowest-precedence rule entry that matches all packets. This entry will match any packets not otherwise processed, so that the user can specify an action to overwrite the default permit action. This lowest-precedence rule entry is usually the last entry in the ACL policy file applied to the interface. Note: When a packet matches more than one rule entry, the highest precedence conflicting action is taken, so you can use the precedence to determine if a packet is permitted or denied. However, incrementing a counter is not a conflicting action, so a packet that matches more that one rule that increments a common Chapter 13. ACLs | 319
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