Administrator Guide

Table 6. L2 and L3 Filtering on Switched Packets (continued)
L2 ACL Behavior L3 ACL Behavior Decision on Targeted Traffic
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.
Using ACL VLAN Groups
Use an ACL VLAN group to optimize ACL CAM usage by minimizing the number of CAM entries when you apply an egress IP
ACL on the member interfaces of specified VLANs.
When you apply an ACL on individual VLANs, the amount of CAM space required increases greatly because the ACL rules are
saved for each VLAN ID. To avoid excessive use of the CAM space, you can configure ACL VLAN groups to combine all VLANs
on which ACL filtering criteria is applied in a single class ID instead of multiple VLAN IDs.
NOTE: CAM optimization applies only when you use an ACL VLAN group; it does not apply if you apply an ACL on individual
VLANs.
Guidelines for Configuring ACL VLAN Groups
Keep the following points in mind when you configure ACL VLAN groups:
● The VLAN member interfaces, on which the ACL in an ACL VLAN group is applied, function as restricted interfaces. The ACL
VLAN group name identifies the group of VLANs on which hierarchical filtering is performed.
● You can add only one ACL to an interface at a time.
● When you apply an ACL VLAN group to a member interface, an error message is displayed if an ACL with different criteria
has already been separately applied to the interface.
● The maximum number of members in an ACL VLAN group is determined by the type of switch and its hardware capabilities.
This scaling limit depends on the number of slices that are allocated for ACL CAM optimization. If one slice is allocated, the
maximum number of VLAN members is 256 for all ACL VLAN groups. If two slices are allocated, the maximum number of
VLAN members is 512 for all ACL VLAN groups.
● The maximum number of VLAN groups that you can configure also depends on the hardware specifications of the switch.
Each VLAN group is mapped to a unique ID in the hardware. The maximum number of ACL VLAN groups supported is 31.
Only a maximum of two components (iSCSI counters, Open Flow, ACL optimization) can be allocated virtual flow processing
slices at a time.
● Port ACL optimization is applicable only for ACLs that are applied without the VLAN range.
● You cannot view the statistical details of ACL rules per VLAN and per interface if you enable the ACL VLAN group capability.
You can view the counters per ACL only by using the show ip accounting access list command.
● On a port, you can apply Layer 2 ACLs on a VLAN or a set of VLANs. In this case, CAM optimization is not applied.
● To enable optimization of CAM space for Layer 2 or Layer 3 ACLs that are applied to ports, the port number is removed as
a qualifier for ACL application on ports, and port bits are used. When you apply the same ACL to a set of ports, the port
bitmap is set when the ACL flow processor (FP) entry is added. When you remove the ACL from a port, the port bitmap is
removed.
● If you do not attach an ACL to any of the ports, the FP entries are deleted. Similarly, when the same ACL is applied on a
set of ports, only one set of entries is installed in the FP, thereby effectively saving CAM space. The optimization is enabled
only if you specify the optimized option with the ip access-group command. This option is not valid for VLAN and LAG
interfaces.
NOTE:
Port-based CAM Optimization is supported only on LM/LP front panel interfaces and is not available on PeGigE
interfaces.
118 Access Control Lists (ACLs)