Match order

The rules in an ACL are sorted in a specific order. When a packet matches a rule, the device stops the match process and performs the action defined in the rule. If an ACL includes overlapping or conflicting rules, the matching result and action to take depend on the rule order.

The following ACL match orders are available:

• config—Sorts ACL rules in ascending order of rule ID. A rule with a lower ID is matched before a rule with a higher ID. If you use this method, check the rules and their order carefully.

	NOTE: The match order of user-defined or WLAN ACLs can only be config.

• auto—Sorts ACL rules in depth-first order. Depth-first ordering makes sure that any subset of a rule is always matched before the rule. Table 1 lists the sequence of tie breakers that depth-first ordering uses to sort rules for each type of ACL.

  Table 1: Sorting ACL rules in depth-first order

A wildcard mask, also called an inverse mask, is a 32-bit binary and represented in dotted decimal notation. In contrast to a network mask, the 0 bits in a wildcard mask represent "do care" bits, and the 1 bits represent "don’t care" bits. If the "do care" bits in an IP address are identical to the "do care" bits in an IP address criterion, the IP address matches the criterion. All "don’t care" bits are ignored. The 0s and 1s in a wildcard mask can be noncontiguous. For example, 0.255.0.255 is a valid wildcard mask.

	NOTE: A simple ACL can include only one rule.