The security administrator needs to manage traffic on a layer 3 device to support FTP from a new remote site. Which of the following would need to be implemented?

Implicit deny is the default behavior at the end of an ACL ruleset, not a standalone configurable feature - it cannot be 'implemented' to manage traffic flows.

VLAN management operates at Layer 2 and segments broadcast domains; it does not filter or control traffic based on protocols or port numbers.

Port security is a Layer 2 switch feature that restricts network access based on MAC addresses, and does not control Layer 3/4 traffic flows by protocol or port.

ACLs are applied to Layer 3 devices (such as routers) and allow administrators to permit or deny traffic based on source/destination IP addresses, protocols, and port numbers - including the specific ports used by FTP (TCP 20 and 21). This enables granular control over which traffic flows are permitted from the remote site. ACLs are the standard mechanism for traffic filtering and policy enforcement on Layer 3 infrastructure.