Reference Guide

For the following features, if you enable counters on rules that have already been configured and a new rule is either
inserted or prepended, all the existing counters are reset:
• L2 ingress access list
• L3 egress access list
• L2 egress access list
If a rule is simply appended, existing counters are not affected.
Table 6. L2 and L3 Filtering on Switched Packets
L2 ACL Behavior L3 ACL Behavior Decision on Targeted Traffic
Deny Deny L3 ACL denies.
Deny Permit L3 ACL permits.
Permit Deny L3 ACL denies.
Permit Permit L3 ACL permits.
NOTE: If you configure an interface as a vlan-stack access port, only the L2 ACL filters the packets. The L3 ACL
applied to such a port does not affect traffic. That is, existing rules for other features (such as trace-list, policy-
based routing [PBR], and QoS) are applied to the permitted traffic.
For information about MAC ACLs, refer to Layer 2.
Assign an IP ACL to an Interface
To pass traffic through a configured IP ACL, assign that ACL to a physical interface, a port channel interface, or a VLAN.
The IP ACL is applied to all traffic entering a physical or port channel interface and the traffic is either forwarded or
dropped depending on the criteria and actions specified in the ACL.
The same ACL may be applied to different interfaces and that changes its functionality. For example, you can take ACL
“ABCD” and apply it using the in keyword and it becomes an ingress access list. If you apply the same ACL using the
out keyword, it becomes an egress access list. If you apply the same ACL to the Loopback interface, it becomes a
Loopback access list.
This section describes the following:
• Configure Ingress ACLs
• Configure Egress ACLs
• Configure ACLs to Loopback
For more information about Layer-3 interfaces, refer to Interfaces.
Applying an IP ACL
To apply an IP ACL (standard or extended) to a physical or port channel interface, use the following commands.
1. Enter the interface number.
CONFIGURATION mode
interface interface slot/port
2. Configure an IP address for the interface, placing it in Layer-3 mode.
INTERFACE mode
ip address ip-address
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