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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.
•
auto
—Sorts ACL rules in depth-first order. Depth-first ordering makes sure any subset of a rule
is always matched before the rule.
lists the sequence of tie breakers that depth-first
ordering uses to sort rules for each type of ACL.
Table 16 Sort ACL rules in depth-first order
ACL category
Sequence of tie breakers
IPv4 basic ACL
1.
More 0s in the source IPv4 address wildcard (more 0s means a
narrower IPv4 address range).
2.
Rule configured earlier.
IPv4 advanced ACL
1.
Specific protocol number.
2.
More 0s in the source IPv4 address wildcard mask.
3.
More 0s in the destination IPv4 address wildcard.
4.
Narrower TCP/UDP service port number range.
5.
Rule configured earlier.
IPv6 basic ACL
1.
Longer prefix for the source IPv6 address (a longer prefix means a
narrower IPv6 address range).
2.
Rule configured earlier.
IPv6 advanced ACL
1.
Specific protocol number.
2.
Longer prefix for the source IPv6 address.
3.
Longer prefix for the destination IPv6 address.
4.
Narrower TCP/UDP service port number range.
5.
Rule configured earlier.
Ethernet frame header
ACL
1.
More 1s in the source MAC address mask (more 1s means a smaller
MAC address).
2.
More 1s in the destination MAC address mask.
3.
Rule configured earlier.
NOTE:
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" 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.
Rule numbering
ACL rules can be manually or automatically numbered.
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.
