Access Control Lists in Action
Learn how ACLs permit or deny traffic by rule.
What an ACL Is
An ACL (Access Control List) is an ordered set of rules that permits or denies traffic based on its characteristics. Routers, switches, and firewalls use ACLs to decide which packets may pass and which are dropped.
Each rule, or ACE (Access Control Entry), matches traffic by criteria like source address, destination, protocol, or port, and applies an action: permit or deny.
What ACLs Match On
A typical ACL rule examines:
- Source IP address (who is sending)
- Destination IP address (where it is going)
- Protocol (TCP, UDP, ICMP)
- Port number (which service)
By combining these, you can write precise rules like permit web traffic to one server while denying everything else, controlling access at a fine level.
All lessons in this course
- The CIA Triad in Networking
- Defense in Depth and Layered Security
- Network Segmentation and Zones
- Access Control Lists in Action