Turbocharge Your IT Journey: Ace the Cisco Certified Network Pro Test 2025 – Network Ninja Style!

When a host has no ARP (Address Resolution Protocol) entry for a specific IP address, it takes action to resolve that address and determine the corresponding MAC (Media Access Control) address. The correct action in this scenario is to make an ARP request.

This process involves the host sending out a broadcast message on the network to all devices, asking, "Who has this IP address? Please send me your MAC address." The device that owns that IP address will respond with its MAC address, allowing the requesting host to create an ARP table entry for future communications. This process is essential because without the MAC address, the host would not be able to encapsulate its network layer packets into link layer frames for transmission over Ethernet or other LAN technologies.

The other choices do not accurately represent the behavior of a host when no ARP entry exists. Waiting for an ICMP response would not help in resolving an IP address to a MAC address. Discarding outgoing packets would hinder communication and is not standard behavior; instead, the host seeks to communicate. Lastly, reverting to a previous entry does not apply in this situation, as there would be no previous entry to revert to when no ARP entry exists.