Originally, access control lists (ACLs) were used for their packet-filtering capabilities, most commonly for IP security filtering. As the IOS software has evolved, the usefulness of ACLs has also grown (depending on the protocols and features supported by IOS) to allow filtering capabilities for all the IOS-supported Layer 3 protocols (and MAC addresses), and traffic TOS and QOS identity services for traffic control tools.
An ACL (or access-list) is a series of action statements used for examining network protocol traffic. There are two possible action statements:
ACLs perform different tasks, depending on how they are applied. After the list is applied, the router's network ...