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Configuring ACLs
Unless otherwise stated, ACLs refer to both IPv4 and IPv6 ACLs throughout this document.
Overview
An access control list (ACL) is a set of rules (or permit or deny statements) for identifying traffic based on
criteria such as source IP address, destination IP address, and port number.
ACLs are essentially used for packet filtering. A packet filter drops packets that match a deny rule and
permits packets that match a permit rule. ACLs are also used by many modules for traffic identification,
for example, QoS and IP routing.
ACL categories
Cate
Basic ACLs 2000 to 2999
IPv4 Source IPv4 address.
IPv6 Source IPv6 address.
Advanced ACLs 3000 to 3999
IPv4
Source/destination IPv4 address, protocols over
IPv4, and other Layer 3 and Layer 4 header fields.
IPv6
Source/destination IPv6 address, protocols over
IPv6, and other Layer 3 and Layer 4 header fields.
Ethernet frame
header ACLs
4000 to 4999
IPv4 and
IPv6
Layer 2 header fields, such as source and destination
MAC addresses, 802.1p priority, and link layer
protocol type.
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 contains 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.
• Auto—Sorts ACL rules in depth-first order. Depth-first ordering makes sure any subset of a rule is
always matched before the rule. Table 134 lists the s
equence of tie breakers that depth-first ordering
uses to sort rules for each type of ACL.
Table 134 Depth-first match for ACLs
ACL cate
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