Reference Guide

100 | Access Control Lists (ACLs)
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Configuring Layer 2 and Layer 3 ACLs on an Interface
Both Layer 2 and Layer 3 ACLs may be configured on an interface in Layer 2 mode. If both L2 and L3
ACLs are applied to an interface, the following rules apply:
• The packets routed by FTOS are governed by the L3 ACL only, since they are not filtered against an
L2 ACL.
• The packets switched by FTOS are first filtered by the L3 ACL, then by the L2 ACL.
• When packets are switched by FTOS, the egress L3 ACL does not filter the packet.
For the following features, if counters are enabled on rules that have already been configured and a new
rule is either inserted or prepended, all the existing counters will be reset:
• L2 Ingress Access list
• L3 Egress Access list
• L2 Egress Access list
If a rule is simply appended, existing counters are not affected.
For information on MAC ACLs, refer to Chapter 22, Layer 2.
Assign an IP ACL to an Interface
Ingress IP ACLs are supported on platforms: c s z
Ingress and Egress IP ACL are supported on platforms: e z
To pass traffic through a configured IP ACL, you must 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.
Table 6-2. L2 and L3 ACL Filtering on Switched Packets
L2 ACL Behavior L3 ACL Behavior Decision on Targeted Traffic
Deny Deny Denied by L3 ACL
Deny Permit Permitted by L3 ACL
Permit Deny Denied by L3 ACL
Permit Permit Permitted by L3 ACL
Note: If an interface is configured as a “vlan-stack access” port, the packets are filtered by an L2 ACL only.
The L3 ACL applied to such a port does not affect traffic. That is, existing rules for other features (such as
trace-list, PBR, and QoS) are applied accordingly to the permitted traffic.