ARP Protocol Layer Classification
The Address Resolution Protocol (ARP) is a Layer 2 protocol. However, because of its function, some may mistaken it with a Layer 3 protocol.
Although ARP includes IP addresses in its messages, these are not used for routing packets to their destinations. Instead, the IP addresses are utilized to identify and determine the Media Access Control (MAC) address of the destination device.
Indeed, ARP messages always remain within the Layer 2 domain (broadcast domain) in which it was generated, except of course if proxy ARP is used.
For this reason, ARP is considered to operate at Layer 2 , meaning it functions at the Data Link layer of the OSI model and is solely focused on the mapping of IP addresses to MAC addresses within a local network segment.
Links
https://networklessons.com/ip-services/arp-address-resolution-protocol-explained