ARP, or Address Resolution Protocol, resides in the Layer 2 of the OSI model, the data link layer. This is because ARP uses broadcast frames at the data link layer to map IP addresses (Layer 3) to MAC addresses (Layer 2). It's crucial for local network communication because devices need MAC addresses to communicate directly. ARP doesn't traverse routers, operating solely within a local network segment.
Several sources confirm this:
- Multiple Cisco Learning Network posts explicitly state that ARP is a Layer 2 protocol. These posts highlight that ARP's function of mapping IP addresses to MAC addresses happens at the data link layer, where MAC addresses are utilized for direct communication.
- Numerous Stack Exchange answers and Reddit discussions reiterate that ARP operates at Layer 2. The consensus is that ARP’s broadcast nature and reliance on MAC addresses firmly place it within the data link layer.
- IBM and Wikipedia documentation also classify ARP as a Layer 2 protocol, emphasizing its role in resolving IP addresses to their corresponding MAC addresses on the local network.
While some discussions might mention ARP's interaction with IP addresses (Layer 3), it's important to note that this interaction doesn't change its fundamental operation at Layer 2. ARP uses Layer 3 information as input to perform its Layer 2 function. It is fundamentally a Layer 2 protocol.
