Which type of ACL should be applied as close to the destination as possible?

The ideal type of ACL to apply close to the destination is a standard ACL. Standard ACLs are used to permit or deny traffic based solely on source IP addresses. When these ACLs are placed near the destination, they can help minimize unnecessary traffic entering the network segments that do not require it, thereby enhancing network efficiency and security.

Positioning standard ACLs close to the destination is particularly effective because it allows for the filtering of unwanted traffic right before reaching the final destination. This strategic placement prevents excessive traffic from consuming bandwidth and processing resources on upstream devices that do not need to handle that traffic.

In contrast, extended ACLs, which filter traffic based on both source and destination IP addresses as well as protocols and ports, are better placed closer to the source of the traffic. This helps in controlling the flow of traffic before it traverses the network unnecessarily. Named ACLs offer a way to manage lists of rules with easier identification but do not necessarily pertain to placement relative to the destination. Dynamic ACLs are often used for temporary access control and typically apply to session-based permissions, making them less relevant to static traffic filtering decisions at the destination.