ACL

ACL stands for Access Control List.

👉 Definition:

An ACL is a set of rules used to control which traffic is allowed or denied on a network device (like a router, switch, or firewall).

In simple terms:

✅ It filters network traffic based on criteria like:

IP address (who is sending or receiving the traffic)

Protocol (like TCP, UDP)

Port number (like HTTP port 80, FTP port 21)

🔹 Types of ACLs:

1. Standard ACL:

Filters traffic only by source IP address.

Simpler and used when you only care who is sending traffic.

Example: Allow traffic from 192.168.1.0 network, block all else.

2. Extended ACL:

Filters by source IP, destination IP, protocol type, and port numbers.

More precise control.

Example: Allow HTTP traffic from 192.168.1.0 to 10.0.0.5, deny everything else.

🔹 Where ACLs are used:

Routers (to control incoming and outgoing traffic)

Firewalls (to secure networks)

Switches (to limit access to VLANs)

🔹 Why ACLs are important:

✅ Improve security by restricting unauthorized access

✅ Optimize network performance by blocking unwanted traffic

✅ Help enforce policies (e.g., only certain devices can access a server)