Install Guide

ip access-list [standard | extended] name
To view which IP ACL is applied to an interface, use the show config command in INTERFACE mode, or use the show
running-config command in EXEC mode.
To filter traffic on Telnet sessions, use only standard ACLs in the access-class command.
Counting ACL Hits
You can view the number of packets matching the ACL by using the count option when creating ACL entries.
1. Create an ACL that uses rules with the count option. Refer to Configure a Standard IP ACL Filter.
2. Apply the ACL as an inbound or outbound ACL on an interface.
3. show ip accounting access-list
EXEC Privilege mode
View the number of packets matching the ACL.
Configure Ingress ACLs
Ingress ACLs are applied to interfaces and to traffic entering the system.
These system-wide ACLs eliminate the need to apply ACLs onto each interface and achieves the same results. By localizing
target traffic, it is a simpler implementation.
To create an ingress ACL, use the ip access-group command in EXEC Privilege mode. The example shows applying the
ACL, rules to the newly created access group, and viewing the access list.
Example of Applying ACL Rules to Ingress Traffic and Viewing ACL Configuration
To specify ingress, use the in keyword. Begin applying rules to the ACL with the ip access-list extended abcd
command. To view the access-list, use the show command.
Configure Egress ACLs
Egress ACLs are applied to line cards and affect the traffic leaving the system. Configuring egress ACLs onto physical interfaces
protects the system infrastructure from attack — malicious and incidental — by explicitly allowing only authorized traffic. These
system-wide ACLs eliminate the need to apply ACLs onto each interface and achieves the same results. By localizing target
traffic, it is a simpler implementation.
To restrict egress traffic, use an egress ACL. For example, when a denial of service (DOS) attack traffic is isolated to a specific
interface, you can apply an egress ACL to block the flow from the exiting the box, thus protecting downstream devices.
To create an egress ACL, use the ip access-group command in EXEC Privilege mode. The example shows viewing the
configuration, applying rules to the newly created access group, and viewing the access list.
NOTE: VRF based ACL configurations are not supported on the egress traffic.
Example of Applying ACL Rules to Egress Traffic and Viewing ACL Configuration
To specify ingress, use the out keyword. Begin applying rules to the ACL with the ip access-list extended abcd
command. To view the access-list, use the show command.
Applying Egress Layer 3 ACLs (Control-Plane)
By default, packets originated from the system are not filtered by egress ACLs.
For example, if you initiate a ping session from the system and apply an egress ACL to block this type of traffic on the interface,
the ACL does not affect that ping traffic. The Control Plane Egress Layer 3 ACL feature enhances IP reachability debugging by
implementing control-plane ACLs for CPU-generated and CPU-forwarded traffic. Using permit rules with the count option, you
can track on a per-flow basis whether CPU-generated and CPU-forwarded packets were transmitted successfully.
1. Apply Egress ACLs to IPv4 system traffic.
Access Control Lists (ACLs)
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