Which statement correctly describes the difference between standard and extended ACLs?

• A. Standard ACLs filter by destination IP; Extended ACLs filter by source IP
• B. Standard ACLs filter by protocol and port; Extended ACLs filter by source IP
• C. Standard ACLs filter by source IP; Extended ACLs filter by protocol, port, and destination
• D. ACLs are only used in firewalls, not routers

Answer: (C)

Standard ACLs are designed to filter traffic based only on where the packet came from—the source IP address. They don’t look at the protocol, ports, or destination, so their control is limited to origin. Extended ACLs give much finer control by examining the protocol (such as TCP, UDP, ICMP), the port numbers for that protocol, and the destination address, allowing you to specify exactly which services to permit or deny to specific destinations. This combination of protocol, port, and destination (with the ability to include source as well) is what sets extended ACLs apart from standard ones, making the statement align with how they differ in practice.