What are the two types of messages used in the Address Resolution Protocol?

In the context of the Address Resolution Protocol (ARP), the two types of messages are indeed the ARP Request and ARP Reply. When a device on a local network wants to discover the MAC address associated with a specific IP address, it sends out an ARP Request message. This message is essentially asking, "Who has this IP address? Please send me your MAC address."

When the device with the matching IP address receives the ARP Request, it responds with an ARP Reply, providing its MAC address back to the original requester. This two-step process enables devices on the same local network to communicate effectively by mapping IP addresses to their respective MAC addresses. Understanding this process is crucial for effective network communication and troubleshooting in IPv4 networks.