[Day 10] 1. Access Control List (ACL)

An Access Control List (ACL) is a set of rules configured on a router to filter and control the flow of network traffic based on specified criteria, such as IP addresses, protocols, or port numbers. ACLs function as security filters, determining which traffic is allowed or blocked based on the defined conditions.

Types of ACLs:

• Standard ACL: Range 1–99, used to filter traffic based solely on the source IP address.
• Extended ACL: Range 100–199, allows filtering based on a combination of source and destination IP addresses, protocols, and port numbers.

Key Features of ACLs:

• Traffic Filtering: ACLs control the flow of network traffic, permitting or denying packets based on factors like IP addresses, protocols, and port numbers.
• Security: ACLs play a vital role in network security by restricting unauthorized traffic and reducing potential attack vectors.
• Interface Application: ACLs must be applied to specific interfaces on a router to filter traffic passing through those interfaces.
• Direction: When configuring an ACL, you must specify the direction of traffic to be filtered—either in (incoming) or out (outgoing).

ACLs are essential for enforcing security policies and ensuring that only authorized traffic can enter or exit a network, effectively preventing unauthorized access and enhancing overall network protection.