If ARP=reply-only is configured on an interface, what will this interface do?

When configuring an interface with ARP set to reply-only, the main function of this setting is to manage how the device interacts with ARP requests. In this mode, the interface will respond to ARP requests for IP addresses that are already listed as static entries in the ARP table. This means that it will only acknowledge requests for specific IP addresses that are predefined, allowing for a level of control over which devices can communicate with the interface.

By accepting only the IP addresses that have been explicitly defined in the '/ip arp' list as static entries, the interface ensures that it does not add any new MAC addresses dynamically. This approach helps maintain a reliable and consistent network by preventing the inclusion of unauthorized devices based on unsolicited ARP requests.

The implications of this configuration are important for network security and management, as it allows network administrators to limit ARP responses to known and trusted devices, minimizing the potential for ARP spoofing and related attacks. Thus, the selected answer correctly describes the interface's acceptance behavior of static entries in the ARP table.