An Access Control List (ACL) is an ordered list of actions the switch performs one by one. Each action is defined by an Access Control Entry (ACE) which specifies the decisions the ACL must perform. These ACEs can perform tasks such as allowing or denying a specific network portion, or a network protocol. A single ACL can have more than one ACE to accomplished a given task. The Sx500 switches can have 512 ACLs and 512 ACEs.
ACLs are of great use in a network since they provide the tools to filter traffic according to the network needs, which makes the network more reliable and efficient.