An ACL is a list of permit or deny rules detailing what can or can’t enter or leave the interface of a router. Every packet that attempts to enter or leave a router must be tested against each rule in the ACL until a match is found. If no match is found, then it will be denied.

There are four types of ACLs that you can use for different purposes, these are standard, extended, dynamic, reflexive, and time-based ACLs.

IP access lists reduce the chance of spoofing and denial-of-service attacks, and allow dynamic, temporary user-access through a firewall. The IP Named Access Control Lists feature gives network administrators the option of using names to identify their access lists.

On Cisco routers, there are two main types: standard and extended. These two types are the most widely used ACLs and the ones I will focus on in this and future articles, but there are some advanced ACLs as well.

The advantages of using access control lists include:

• Better protection of internet-facing servers.
• More control of access through entry points.
• More control of access to and traffic between internal networks.
• More granular control of user and group permissions.

Access-list (ACL) is a set of rules defined for controlling network traffic and reducing network attacks. ACLs are used to filter traffic based on the set of rules defined for the incoming or outgoing of the network.

An access control list (ACL) contains rules that grant or deny access to certain digital environments. There are two types of ACLs: Filesystem ACLs━filter access to files and/or directories. Filesystem ACLs tell operating systems which users can access the system, and what privileges the users are allowed.

By controlling how many users can access certain files or systems, access control lists limit network traffic and in turn increase network performance. This saves companies money because they can get the most out of their current network instead of spending to upgrade and increase their network regularly.

– Advantage: ∗ Easy to know the access right of a given subject. ∗ Easy to revoke a users access right on all objects. – Disadvantage: ∗ Difficult to know who can access a given object. ∗ Difficult to revoke all access right to an object.

CCNA™: Access Control Lists The Cisco Access Control List (ACL) is are used for filtering traffic based on a given filtering criteria on a router or switch interface. Based on the conditions supplied by the ACL, a packet is allowed or blocked from further movement.

In all software releases, the access-list-number can be 100 to 199. In Cisco IOS Software Release 12.0.1, extended ACLs begin to use additional numbers (2000 to 2699). These additional numbers are referred to as expanded IP ACLs. Cisco IOS Software Release 11.2 added the ability to use list name in extended ACLs.

A Standard Access List allows you to permit or deny traffic FROM specific IP addresses. The destination of the packet and the ports involved can be anything. This is the command syntax format of a standard ACL. access-list 10 permit 192.168.2.0 0.0.0.255

An access control list (ACL) consists of one or more access control entries (ACEs) that collectively define the network traffic profile. This profile can then be referenced by Cisco IOS XR Software software features such as traffic filtering, priority or custom queueing, and dynamic access control.