Yes, ARP (Address Resolution Protocol) is only on LAN (Local Area Network). According to our reference, ARP is a Data Link Layer protocol that operates solely on the local area network or point-to-point link to which a host is directly connected. This means ARP's scope is limited to resolving IP addresses to MAC addresses within the same network segment.
Here's a breakdown:
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ARP's Function: ARP resolves IP addresses to MAC addresses, enabling communication between devices on the same local network.
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LAN Limitation: ARP packets are not routable. They are broadcast within a LAN and are not forwarded by routers to other networks. Routers use their own ARP processes for each connected network.
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Data Link Layer Protocol: As a Data Link Layer protocol, ARP's functionality is intrinsically tied to the physical network segment.
Consider this example:
Imagine two computers, Computer A and Computer B, connected to the same LAN. Computer A wants to send a packet to Computer B.
- Computer A knows Computer B's IP address but needs its MAC address.
- Computer A broadcasts an ARP request: "Who has IP address [Computer B's IP address]? Tell [Computer A's MAC address]."
- Computer B receives the ARP request and responds with its MAC address.
- Computer A now has Computer B's MAC address and can send the packet.
This process only works because both computers are on the same LAN. If Computer B were on a different network, Computer A would instead ARP for the MAC address of its default gateway (router).
In summary, ARP is fundamentally designed for local network operations. It cannot function across different networks separated by routers.
