Which statement regarding ARP=reply-only on a router interface is correct?

In the context of router configurations, setting an interface's ARP to "reply-only" indicates that the router will respond to ARP requests that it receives, but it will not actively create dynamic ARP entries for devices. Instead, it only allows for the updates of existing entries based on incoming ARP requests. This means that while the router can respond, it does not learn new MAC address-to-IP address mappings dynamicically, which would be the case if dynamic ARP entries were permitted.

Therefore, with the "reply-only" setting in place, the router strictly maintains a static ARP table. Under this configuration, any required IP to MAC address mappings must be added manually or created as static entries. This is why it's accurate to say that the configuration does not allow for dynamic ARP entries to be established on the router interface. Knowledge of this aspect can significantly impact network operations and security, as it implies a controlled environment where only pre-defined relationships are recognized and used by the router.