ACL (Access Control Lists)

Hi everyone, on today we are going to learn about ACL (i.e, Access Control Lists) in simplified terms and how ACL works with an example.

In simple points, ACL  ;

• There are filters that enable you to control which routing updates or packets are permitted or denied in or out of a network.
• They are specifically used by network administrators to filter traffic and to provide extra security for the network (i.e., This can be applied to Cisco routers).
• ACLs provide a powerful way to control traffic into and out of your network 
• This control can be as simple as permitting or denying network hosts or addresses.

How it works ? explained below in simplified format with example ;

A router acts as a packet filter when it forwards or denies packets according to filtering rules. As a Layer 3 device, a packet-filtering router uses rules to determine whether to permit or deny traffic based on source and destination IP addresses, source port and destination port, and the protocol of the packet.

To simplify this note, how ACL or a router uses packet filtering works with a example given below.

Example: Imagine a guard stationed at a locked door. The guard’s instruction is to allow only people whose names appear on a guest list to pass through the door. The guard is filtering people based on the condition of having their names on the authorized list.

When a packet arrives at the router, the router extracts certain information from the packet header and makes decisions according to the filter rules as to whether the packet can pass through or be dropped.

Packet filtering process works at the Network layer of the Open Systems Interconnection (OSI) model or the Internet layer of TCP/IP.

Watch this video given below by click this PLAY > button to see about extended ACL configuration how of our CCNA Lab. Also make sure to share and subscribe our channel.