4000 Router Series ACL and QoS Configuration Guide

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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. If you use this method, carefully check the rules and their order.

NOTE:

The match order of user-defined ACLs can only be config.

• 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 1 lists the

sequence of tie breakers that depth-first ordering

uses to sort rules for each type of ACL.

Table 1 Sort ACL rules in depth-first order

ACL cate

uence of tie breakers

IPv4 basic ACL

1. VPN instance

2. More 0s in the source IPv4 address wildcard (more 0s means a narrower

IPv4 address range)

3. Rule configured earlier

IPv4 advanced ACL

4. VPN instance.

5. Specific protocol number.

6. More 0s in the source IPv4 address wildcard mask.

7. More 0s in the destination IPv4 address wildcard.

8. Narrower TCP/UDP service port number range.

9. Rule configured earlier.

IPv6 basic ACL

10. VPN instance.

11. Longer prefix for the source IPv6 address (a longer prefix means a narrower

IPv6 address range).

12. Rule configured earlier.

IPv6 advanced ACL

13. VPN instance.

14. Specific protocol number.

15. Longer prefix for the source IPv6 address.

16. Longer prefix for the destination IPv6 address.

17. Narrower TCP/UDP service port number range.

18. Rule configured earlier.

Ethernet frame header ACL

19. More 1s in the source MAC address mask (more 1s means a smaller MAC

address).

20. More 1s in the destination MAC address mask.

21. Rule configured earlier.

A wildcard mask, also called an inverse mask, is a 32-bit binary number 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"