What is the primary difference between standard and extended ACLs?

The primary difference between standard and extended ACLs lies in the filtering capabilities related to source IP addresses. Standard ACLs function by filtering traffic based solely on the source IP address. This means that when a standard ACL is applied, it can permit or deny traffic depending solely on the origin of the packets, without considering other parameters such as destination IP addresses, protocols, or port numbers.

On the other hand, extended ACLs offer more granular control and can filter traffic based on a combination of source and destination IP addresses, as well as protocols (like TCP or UDP) and port numbers. This broad filtering capability allows for more complex and specific traffic management, enabling network administrators to define rules that cater to various traffic types and requirements.

Thus, the focus of standard ACLs on the source IP address is what establishes this fundamental distinction from extended ACLs, making the correct option the one that highlights this point.