KB.15.15

entry (permit or drop the packet) and no further comparisons of the packet are made with the

remaining ACEs in the list.

This means that when an ACE whose criteria matches a packet is found, the action configured for

that ACE is invoked, and any remaining ACEs in the ACL are ignored. Because of this sequential

processing, successfully implementing an ACL depends in part on configuring ACEs in the correct

order for the overall policy you want the ACL to enforce.

Figure 229 The packet-filtering process in an ACL with N entries (ACEs)

NOTE: The order in which an ACE occurs in an ACL is significant.

For example, if an ACL contains six ACEs, but the first ACE allows Permit Any forwarding, then

the ACL permits all IPv4 traffic, and the remainingACEs in the list do not apply, even if they specify

criteria that would make a match with any of the traffic permitted by the first ACE.

For example, suppose you want to configure an ACL on the switch (with an ID of "Test-02") to

invoke these policies for routed traffic entering the switch on VLAN 12:

1. Permit inbound IPv4 traffic from IP address 10.11.11.42.

2. Deny only the inbound Telnet traffic from address 10.11.11.101.

3. Permit only inbound Telnet traffic from IP address 10.11.11.33.

4. Deny all other inbound IPv4 traffic.

The following ACL model , when assigned to inbound filtering on an interface, supports the above

case:

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