ACL is an acronym for Access Control Lists. It is a set of rules used to control the network traffic and reduce network attacks. ACL works as a network filter and can only be configured on devices with packet filtering capabilities such as routers. The primary purpose of using an ACL is to provide network security. It contains a set of conditions that are applied on an interface basis to determine whether to allow or deny network traffic entering or leaving a network interface. The best place to configure an ACL is on the edge router that acts as a gateway for all outside networks. There are four types of ACLs based on their usage –
* Standard ACL
* Extended ACL
* Dynamic ACL
* Reflexive ACL
