What is the difference between a standard and an extended ACL?

Standard Access Control Lists (ACLs) are the simpler of the two. They filter traffic based solely on the source IP address. This makes them suitable for basic filtering tasks, like blocking or allowing traffic from specific IP addresses.

Extended ACLs, on the other hand, offer more granular control. They can filter traffic based on a wider range of criteria, including:

Source IP address
Destination IP address
Protocol type (e.g., TCP, UDP, ICMP)
Source and destination port numbers

This flexibility makes extended ACLs ideal for more complex filtering scenarios, such as :

Restricting access to specific services: For example, blocking all incoming traffic except for HTTP (port 80) and HTTPS (port 443).
Implementing firewalls: Creating rules to allow or deny traffic based on multiple criteria.
Prioritizing traffic: Giving preference to certain types of traffic, such as VoIP.

In essence :

Standard ACLs are like a basic sieve, filtering traffic based on a single criterion.
Extended ACLs are like a fine-mesh sieve, capable of filtering traffic based on multiple criteria.

Which one should you use?

The choice between standard and extended ACLs depends on your specific needs. If you need to perform simple filtering tasks, a standard ACL may suffice. However, if you require more granular control over network traffic, an extended ACL is the way to go.

Note: Both standard and extended ACLs can be applied to routers and firewalls to control network traffic.